Attainment of National Ambient Air Quality Standard-NAAQS for exposure limits to air pollutants is of great concern to State and Local agencies and communities in the United State because of potential health impacts. This is particularly important and challenging in urban areas because of high population densities and complex terrain. Exceedances of NAAQS requires states to develop implementation plans to address them and as such, studying the horizontal and vertical distribution and mixing of pollutants is key to understanding their transport and evolution. In this study, vertical and scanning horizontal lidar measurements together with in situ observations from particulate matter and trace gas analyzers from state air quality networks are used to shed light on mechanisms that impact movement of aerosol, including emissions from power generating stations at periods of high electricity demand.
In this study, multiple remote sensing and in-situ measurements are combined in order to obtain a comprehensive
understanding of the aerosol distribution in New York City. Measurement of the horizontal distribution of aerosols is
performed using a scanning eye-safe elastic-backscatter micro-pulse lidar. Vertical distribution of aerosols is measured
with a co-located ceilometer. Furthermore, our analysis also includes in-situ measurements of particulate matter and
wind speed and direction. These observations combined show boundary layer dynamics as well as transport and
inhomogeneous spatial distribution of aerosols, which are of importance for air quality monitoring.
In this paper, we present two signal processing algorithms implemented using the FPGA. The first algorithm involves explicate time gating of received signals that correspond to a desired spatial resolution, performing a Fast Fourier Transform (FFT) calculation on each individual time gate, taking the square modulus of the FFT to form a power spectrum and then accumulating these power spectra for 10k return signals. The second algorithm involves calculating the autocorrelation of the backscattered signals and then accumulating the autocorrelation for 10k pulses. Efficient implementation of each of these two signal processing algorithms on an FPGA is challenging because it requires there to be tradeoffs between retaining the full data word width, managing the amount of on chip memory used and respecting the constraints imposed by the data width of the FPGA. A description of the approach used to manage these tradeoffs for each of the two signal processing algorithms are presented and explained in this article. Results of atmospheric measurements obtained through these two embedded programming techniques are also presented.
Two FPGA embedded programming approaches are considered and compared for a 20 kHz pulse repetition rate
coherent Doppler lidar system which acquires return signals at 400 Msamples/second and operates with signal to noise
ratios as low as -20 dB. In the first approach, the acquired return signal is gated in time and the square modulus of the
fast Fourier transform is accumulated for each of the range gates, producing a series of power spectra as a function of
range. Wind speed decisions based on numerical estimators can then be made after transferring the range gated
accumulated power spectra to a host computer, enabling the line of sight wind speed as a function of range gate to be
calculated and stored for additional processing. In the second FPGA approach, a digital IQ demodulator and down
sampler reduces the data flow requirements so that an autocorrelation matrix representing a pre-selected number of lags
can be accumulated, allowing for the process of range gating to be explored on the host computer. The added feature of
the second approach is that it allows for an additional capability to adjust the range gate period dynamically as the state
of the atmospheric boundary layer (e.g. backscatter coefficient and stability condition) changes. A simple manual beam
scanning technique is used to calculate the wind field vector which is graphically displayed on time-height cross section
plots. A comparison to other observed and modeled information is presented suggesting the usefulness for the
characterization of microscale meteorology.
KEYWORDS: Signal processing, Field programmable gate arrays, LIDAR, Doppler effect, Wind measurement, Data acquisition, Signal detection, Remote sensing, Bragg cells, Digital signal processing
A field deployable all-fiber eye-safe Coherent Doppler LIDAR is being developed at the Optical Remote Sensing
Lab at the City College of New York (CCNY) and is designed to monitor wind fields autonomously and
continuously in urban settings. Data acquisition is accomplished by sampling lidar return signals at 400 MHz and
performing onboard processing using field programmable gate arrays (FPGAs). The FPGA is programmed to
accumulate signal information that is used to calculate the power spectrum of the atmospherically back scattered
signal. The advantage of using FPGA is that signal processing will be performed at the hardware level, reducing the
load on the host computer and allowing for 100% return signal processing. An experimental setup measured wind
speeds at ranges of up to 3 km.
A compact coherent wind lidar system has been developed and is being tested in an urban environment. We use
polarization maintaining fiber throughout the system to improve the stability of the heterodyne detected return signal.
The 1.54 micron transmitter is designed using a master oscillator and pulsed power amplifier configuration. The
receiver is operated in a coaxial arrangement and balanced detection is employed to reduce the effects of relative
intensity noise, allowing for operation in the shot noise limited regime. Development and verification of the lidar system
is enhanced by taking advantage of a set of ground based sodar, radar wind profiler and building top anemometers that
are part of the New York City Meteorological Network. Operation in a coastal urban environment with a complex
terrain such as New York City requires that the system be flexible enough to allow for adjustable operating conditions,
tunable signal processing algorithms and user defined data products, so that the optimal performance can be chosen with
a variety of practical applications in mind.
The Department of Homeland Security (DHS) sponsored Urban Dispersion Program (UDP) resulted in the strategic
placement of weather instruments in New York City (NYC) and the transition of some instruments to the City College of
New York (CCNY) operated NYC MetNet to provide timely and accurate information on "skimming field" winds above
city building tops. In order to extend the observational capabilities of the NYC MetNet, a cost effective portable eye
safe fiber optic based coherent wind lidar system is currently under development in CCNY laboratories. Wind lidar
measurements, coupled with the continuous observations from the NYC MetNet, should support the initialization,
feedback and development of plume models that would be used after an initial detection of airborne toxins. An
overview of the lidar system design and the NYC MetNet will be given.
Optical fiber parametric amplification is combined with Raman amplification to demonstrate the possibility of extending
the flat gain bandwidth of Raman fiber amplifiers. Counter propagating pumps separated by over 145 nm are used to
pump a section of highly nonlinear fiber. Parametric gain enables an increase in the gain bandwidth by extending the
gain region to the long wavelength side of the Raman gain. Gains of nearly 20 dB have been achieved with this
configuration. To achieve gain flatness of 5-6 dB, lower peak gains of between 8 and 14 dB are observed where the
variations of the gain and gain flatness are controlled by adjusting the two pump powers. Optimal pump powers are
determined that result in good performance amplification by characterizing the receiver power penalty of bit error rate
measurements. Negligible power penalty is observed in the region of strong Raman gain whereas nearly a 3 dB power
penalty is observed in the region of strong parametric gain. An experimental technique is proposed that helps in the
understanding of the coupling of the parametric and Raman processes.
KEYWORDS: Network architectures, Receivers, Transmitters, Signal detection, Stars, Multiplexing, Signal processing, Broadband telecommunications, Failure analysis, Process control
To date, the mainstream Ethernet Passive Optical Network (EPON) bandwidth allocation schemes as well as the new IEEE 802.3ah Ethernet in the First Mile (EFM) Task Force specifications have been centralized, relying on a component in the central office, Optical Line Termination (OLT), to provision upstream traffic. Hence, the OLT is the only device that can arbitrate time-division access to the shared channel. Since the OLT has global knowledge of the state of the entire network, this is a centralized control plane in which the OLT has centralized intelligence. One of the major problems associated with a centralized architecture is the "single-point of failure" problem that is the failure of the OLT software will bring down the whole access network. It is the purpose of this work to propose a distributed solution to this problem, and to devise and experimentally demonstrate the feasibility of implementing a novel Ethernet over Star Coupler-based PON architecture that uses a fully distributed time division multiple access arbitration schemes. Specifically, we assess the viability of implementing a distributed control plane architecture that facilitates internetworking among connected users.
In addition to the added flexibility and reliability associated with distributed control plane architecture, as well as emulating shared LAN capability among different users, the distributed networking architecture and the associated bandwidth allocation algorithms have characteristics that make them far better suited for provisioning Quality of Service (QoS) schemes necessary for multimedia services over a single line.
A new optical packet switching network and its enabling technologies are investigated for implementation in a Petaflops scale supercomputer system. We capitalize on the immense bandwidth of the optical fiber interconnects by deploying WDM/TDM packet payloads. To accommodate current optical switching technologies, the routing operations in the network are drastically simplified and the need for buffering is completely eliminated. This paper presents the experimental demonstration of the routing within the unique packet switched architecture. Multiple node hops are demonstrated in a node test-bed environment with a re- circulating loop configuration.
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