27,112 research outputs found
Nanosecond channel-switching exact optical frequency synthesizer using an optical injection phase-locked loop (OIPLL)
Experimental results are reported on an optical frequency synthesizer for use in dynamic dense wavelength-division-multiplexing networks, based on a tuneable laser in an optical injection phase-locked loop for rapid wavelength locking. The source combines high stability (50 dB), narrow linewidth (10 MHz), and fast wavelength switching (<10 ns)
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Noise shaping Asynchronous SAR ADC based time to digital converter
Time-to-digital converters (TDCs) are key elements for the digitization of timing information in modern mixed-signal circuits such as digital PLLs, DLLs, ADCs, and on-chip jitter-monitoring circuits. Especially, high-resolution TDCs are increasingly employed in on-chip timing tests, such as jitter and clock skew measurements, as advanced fabrication technologies allow fine on-chip time resolutions. Its main purpose is to quantize the time interval of a pulse signal or the time interval between the rising edges of two clock signals. Similarly to ADCs, the performance of TDCs are also primarily characterized by Resolution, Sampling Rate, FOM, SNDR, Dynamic Range and DNL/INL. This work proposes and demonstrates 2nd order noise shaping Asynchronous SAR ADC based TDC architecture with highest resolution of 0.25 ps among current state of art designs with respect to post-layout simulation results. This circuit is a combination of low power/High Resolution 2nd Order Noise Shaped Asynchronous SAR ADC backend with simple Time to Amplitude converter (TAC) front-end and is implemented in 40nm CMOS technology. Additionally, special emphasis is given on the discussion on various current state of art TDC architectures.Electrical and Computer Engineerin
A GHz-range, High-resolution Multi-modulus Prescaler for Extreme Environment Applications
The generation of a precise, low-noise, reliable clock source is critical to developing mixed-signal and digital electronic systems. The applications of such a clock source are greatly expanded if the clock source can be configured to output different clock frequencies. The phase-locked loop (PLL) is a well-documented architecture for realizing this configurable clock source. Principle to the configurability of a PLL is a multi-modulus divider. The resolution of this divider (or prescaler) dictates the resolution of the configurable PLL output frequency. In integrated PLL designs, such a multi-modulus prescaler is usually sourced from a GHz-range voltage-controlled oscillator. Therefore, a fully-integrated PLL ASIC requires the development of a high-speed, high-resolution multi-modulus prescaler.
The design challenges associated with developing such a prescaler are compounded when the application requires the device to operate in an extreme environment. In these extreme environments (often extra-terrestrial), wide temperature ranges and radiation effects can adversely affect the operation of electronic systems. Even more problematic is that extreme temperatures and ionizing radiation can cause permanent damage to electronic devices. Typical commercial-off-the-shelf (COTS) components are not able withstand such an environment, and any electronics operating in these extreme conditions must be designed to accommodate such operation.
This dissertation describes the development of a high-speed, high-resolution, multi-modulus prescaler capable of operating in an extreme environment. This prescaler has been developed using current-mode logic (CML) on a 180-nm silicon-germanium (SiGe) BiCMOS process. The prescaler is capable of operating up to at least 5.4 GHz over a division range of 16-48 with a total of 27 configurable moduli. The prescaler is designed to provide excellent ionizing radiation hardness, single-event latch-up (SEL) immunity, and single-event upset (SEU) resistance over a temperature range of â180°C to 125°C
Phase-locking of two self-seeded tapered amplifier lasers
We report on the phase-locking of two diode lasers based on self-seeded
tapered amplifiers. In these lasers, a reduction of linewidth is achieved using
narrow-band high-transmission interference filters for frequency selection. The
lasers combine a compact design with a Lorentzian linewidth below 200 kHz at an
output power of 300 mW. We characterize the phase noise of the phase-locked
laser system and study its potential for coherent beam-splitting in atom
interferometers.Comment: 7 pages, 4 figure
Cascaded multiplexed optical link on a telecommunication network for frequency dissemination
We demonstrate a cascaded optical link for ultrastable frequency
dissemination comprised of two compensated links of 150 km and a repeater
station. Each link includes 114 km of Internet fiber simultaneously carrying
data traffic through a dense wavelength division multiplexing technology, and
passes through two routing centers of the telecommunication network. The
optical reference signal is inserted in and extracted from the communication
network using bidirectional optical add-drop multiplexers. The repeater station
operates autonomously ensuring noise compensation on the two links and the
ultra-stable signal optical regeneration. The compensated link shows a
fractional frequency instability of 3 \times 10-15 at one second measurement
time and 5 \times 10-20 at 20 hours. This work paves the way to a wide
dissemination of ultra-stable optical clock signals between distant
laboratories via the Internet network
Harnessing optical micro-combs for microwave photonics
In the past decade, optical frequency combs generated by high-Q
micro-resonators, or micro-combs, which feature compact device footprints, high
energy efficiency, and high-repetition-rates in broad optical bandwidths, have
led to a revolution in a wide range of fields including metrology, mode-locked
lasers, telecommunications, RF photonics, spectroscopy, sensing, and quantum
optics. Among these, an application that has attracted great interest is the
use of micro-combs for RF photonics, where they offer enhanced functionalities
as well as reduced size and power consumption over other approaches. This
article reviews the recent advances in this emerging field. We provide an
overview of the main achievements that have been obtained to date, and
highlight the strong potential of micro-combs for RF photonics applications. We
also discuss some of the open challenges and limitations that need to be met
for practical applications.Comment: 32 Pages, 13 Figures, 172 Reference
Highly tunable repetition-rate multiplication of mode-locked lasers using all-fibre harmonic injection locking
Higher repetition-rate optical pulse trains have been desired for various
applications such as high-bit-rate optical communication, photonic
analogue-to-digital conversion, and multi- photon imaging. Generation of multi
GHz and higher repetition-rate optical pulse trains directly from mode-locked
oscillators is often challenging. As an alternative, harmonic injection locking
can be applied for extra-cavity repetition-rate multiplication (RRM). Here we
have investigated the operation conditions and achievable performances of
all-fibre, highly tunable harmonic injection locking-based pulse RRM. We show
that, with slight tuning of slave laser length, highly tunable RRM is possible
from a multiplication factor of 2 to >100. The resulting maximum SMSR is 41 dB
when multiplied by a factor of two. We further characterize the noise
properties of the multiplied signal in terms of phase noise and relative
intensity noise. The resulting absolute rms timing jitter of the multiplied
signal is in the range of 20 fs to 60 fs (10 kHz - 1 MHz) for different
multiplication factors. With its high tunability, simple and robust all-fibre
implementation, and low excess noise, the demonstrated RRM system may find
diverse applications in microwave photonics, optical communications, photonic
analogue-to-digital conversion, and clock distribution networks.Comment: 25 pages, 9 figure
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