864 research outputs found
Generation of tunable, high repetition rate optical frequency combs using on-chip silicon modulators
We experimentally demonstrate tunable, highly-stable frequency combs with
high repetition-rates using a single, charge injection based silicon PN
modulator. In this work, we demonstrate combs in the C-band with over 8 lines
in a 20-dB bandwidth. We demonstrate continuous tuning of the center frequency
in the C-band and tuning of the repetition-rate from 7.5GHz to 12.5GHz. We also
demonstrate through simulations the potential for bandwidth scaling using an
optimized silicon PIN modulator. We find that, the time varying free carrier
absorption due to carrier injection, an undesirable effect in data modulators,
assists here in enhancing flatness in the generated combs.Comment: 10 pages, 7 figure
Generation of very flat optical frequency combs from continuous-wave lasers using cascaded intensity and phase modulators driven by tailored radio frequency waveforms
We demonstrate a scheme, based on a cascade of lithium niobate intensity and
phase modulators driven by specially tailored radio frequency waveforms to
generate an optical frequency comb with very high spectral flatness. In this
work we demonstrate a 10 GHz comb with ~40 lines with spectral power variation
below 1-dB and ~60 lines in total. The number of lines that can be generated is
limited by the power handling capability of the phase modulator, and this can
be scaled without compromising the spectral flatness. Furthermore, the spectral
phase of the generated combs in our scheme is almost purely quadratic which, as
we will demonstrate, allows for very high quality pulse compression using only
single mode fiber.Comment: 12 pages, 3 figures, replaced the older version with the published
versio
Coherent terabit communications with microresonator Kerr frequency combs
Optical frequency combs enable coherent data transmission on hundreds of
wavelength channels and have the potential to revolutionize terabit
communications. Generation of Kerr combs in nonlinear integrated microcavities
represents a particularly promising option enabling line spacings of tens of
GHz, compliant with wavelength-division multiplexing (WDM) grids. However, Kerr
combs may exhibit strong phase noise and multiplet spectral lines, and this has
made high-speed data transmission impossible up to now. Recent work has shown
that systematic adjustment of pump conditions enables low phase-noise Kerr
combs with singlet spectral lines. Here we demonstrate that Kerr combs are
suited for coherent data transmission with advanced modulation formats that
pose stringent requirements on the spectral purity of the optical source. In a
first experiment, we encode a data stream of 392 Gbit/s on subsequent lines of
a Kerr comb using quadrature phase shift keying (QPSK) and 16-state quadrature
amplitude modulation (16QAM). A second experiment shows feedback-stabilization
of a Kerr comb and transmission of a 1.44 Tbit/s data stream over a distance of
up to 300 km. The results demonstrate that Kerr combs can meet the highly
demanding requirements of multi-terabit/s coherent communications and thus
offer a solution towards chip-scale terabit/s transceivers
Photonic RF and microwave reconfigurable filters and true time delays based on an integrated optical Kerr frequency comb source
We demonstrate advanced transversal radio frequency (RF) and microwave
functions based on a Kerr optical comb source generated by an integrated
micro-ring resonator. We achieve extremely high performance for an optical true
time delay aimed at tunable phased array antenna applications, as well as
reconfigurable microwave photonic filters. Our results agree well with theory.
We show that our true time delay would yield a phased array antenna with
features that include high angular resolution and a wide range of beam steering
angles, while the microwave photonic filters feature high Q factors, wideband
tunability, and highly reconfigurable filtering shapes. These results show that
our approach is a competitive solution to implementing reconfigurable, high
performance and potentially low cost RF and microwaveComment: 15 pages, 11 Figures, 60 Reference
High performance photonic microwave filters based on a 50GHz optical soliton crystal Kerr micro-comb
We demonstrate a photonic radio frequency (RF) transversal filter based on an
integrated optical micro-comb source featuring a record low free spectral range
of 49 GHz yielding 80 micro-comb lines across the C-band. This record-high
number of taps, or wavelengths for the transversal filter results in
significantly increased performance including a QRF factor more than four times
higher than previous results. Further, by employing both positive and negative
taps, an improved out-of-band rejection of up to 48.9 dB is demonstrated using
Gaussian apodization, together with a tunable centre frequency covering the RF
spectra range, with a widely tunable 3-dB bandwidth and versatile dynamically
adjustable filter shapes. Our experimental results match well with theory,
showing that our transversal filter is a competitive solution to implement
advanced adaptive RF filters with broad operational bandwidths, high frequency
selectivity, high reconfigurability, and potentially reduced cost and
footprint. This approach is promising for applications in modern radar and
communications systems.Comment: 19 pages, 12 figures, 107 reference
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