15 research outputs found
Broadband quantum-dot frequency-modulated comb laser
Frequency-modulated (FM) laser combs, which offer a periodic
quasi-continuous-wave output and a flat-topped optical spectrum, are emerging
as a promising solution for wavelength-division multiplexing applications,
precision metrology, and ultrafast optical ranging. The generation of FM combs
relies on spatial hole burning, group velocity dispersion (GVD), Kerr
nonlinearity, and four-wave mixing (FWM). While FM combs have been widely
observed in quantum cascade Fabry-Perot (FP) lasers, the requirement for a
low-dispersion FP cavity can be a challenge in platforms where the waveguide
dispersion is mainly determined by the material. Here we report a 60 GHz
quantum-dot (QD) mode-locked laser in which both the amplitude-modulated (AM)
and the FM comb can be generated independently. The high FWM efficiency of -5
dB allows the QD laser to generate an FM comb efficiently. We also demonstrate
that the Kerr nonlinearity can be practically engineered to improve the FM comb
bandwidth without the need for GVD engineering. The maximum 3-dB bandwidth that
our QD platform can deliver is as large as 2.2 THz. This study gives novel
insights into the improvement of FM combs and paves the way for
small-footprint, electrically-pumped, and energy-efficient frequency combs for
silicon photonic integrated circuits (PICs)
Subspace tracking for independent phase noise source separation in frequency combs
Advanced digital signal processing techniques in combination with
ultra-wideband balanced coherent detection have enabled a new generation of
ultra-high speed fiber-optic communication systems, by moving most of the
processing functionalities into digital domain. In this paper, we demonstrate
how digital signal processing techniques, in combination with ultra-wideband
balanced coherent detection can enable optical frequency comb noise
characterization techniques with novel functionalities. We propose a
measurement method based on subspace tracking, in combination with
multi-heterodyne coherent detection, for independent phase noise sources
identification, separation and measurement. Our proposed measurement technique
offers several benefits. First, it enables the separation of the total phase
noise associated with a particular comb-line or -lines into multiple
independent phase noise terms associated with different noise sources. Second,
it facilitates the determination of the scaling of each independent phase noise
term with comb-line number. Our measurement technique can be used to: identify
the most dominant source of phase noise; gain a better understanding of the
physics behind the phase noise accumulation process; and confirm, already
existing, and enable better phase noise models. In general, our measurement
technique provides new insights into noise behavior of optical frequency combs
Attenuation Scale Calibration of an Optical Time Domain Reflectometer Using an External Laser Source
Distance Scale Calibration of Optical Time Domain Reflectometer Using Active Intensity Modulation
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Broadband quantum-dot frequency-modulated comb laser.
Frequency-modulated (FM) laser combs, which offer a quasi-continuous-wave output and a flat-topped optical spectrum, are emerging as a promising solution for wavelength-division multiplexing applications, precision metrology, and ultrafast optical ranging. The generation of FM combs relies on spatial hole burning, group velocity dispersion, Kerr nonlinearity, and four-wave mixing (FWM). While FM combs have been widely observed in quantum cascade Fabry-Perot (FP) lasers, the requirement for a low-dispersion FP cavity can be a challenge in platforms where the waveguide dispersion is mainly determined by the material. Here we report a 60 GHz quantum-dot (QD) mode-locked laser in which both the amplitude-modulated (AM) and the FM comb can be generated independently. The high FWM efficiency of -5 dB allows the QD laser to generate FM comb efficiently. We also demonstrate that the Kerr nonlinearity can be practically engineered to improve the FM comb bandwidth without the need for GVD engineering. The maximum 3-dB bandwidth that our QD platform can deliver is as large as 2.2 THz. This study gives novel insights into the improvement of FM combs and paves the way for small-footprint, electrically pumped, and energy-efficient frequency combs for silicon photonic integrated circuits (PICs)