196,122 research outputs found
RSOA-based self-seeded transmitters: The ERMES project results and offsprings
No full textThe EU FP7 ERMES project focused on the development of a wavelength division multiplexed passive optical network (WDM PON) colourless self-tuning transmitter based on reflective semiconductor optical amplifiers (RSOAs) self-seeding. These transmitters represent low cost solutions to achieve self-organized wavelength access networks. The EU ERMES project developed self-tuning transmitters both in the C- and O- band with tens of kilometres reach up to 10 Gb/s. During the project we developed different self-seeding architectures with single RSOA exploitation (standard self-seeding) or two-RSOA exploitation (amplified or face-to-face self-seeding). The employment of Faraday rotators and mirrors in retracing configurations ensured polarization insensitive operation of the self-seeded architectures allowing for the exploitation of high gain C and O-band RSOAs, which present a very high polarization dependent gain. The project evaluated the coexistence of time division multiplexing (TDM) and WDM PON supporting high-numbers of users: although the burst mode operation was limited by the build-up time of the long-cavity laser, the rise time is compatible with a sleep mode for energy saving. After the project conclusion self-seeded transmitters have been exploited with alternative modulation formats including polarization division multiplexing and frequency division multiplexing in order to increase the achievable bit rates. Finally further studies to increase modulation cancellation inside self-seeded transmitters have been performed
An Alternative to Commercial Optical Fibre Sensors for Shallow Landslide Monitoring – Interferometric Optical Fibre Sensing
No full textOptical fibre-based monitoring has settled in the field of geohazards monitoring. Interferometric optical fibre sensors are the least used in landslide monitoring, while classical approaches rely on Fibre Bragg Grating and Brillouin Optical Time Domain Reflectometry/Analysis. Landslide monitoring goes hand by hand with the development of technology. While authors tend to focus on the unprecedented accuracy and reduced costs of the sensor itself, the economic and practical aspects related to the interrogating systems are often disregarded. Recently, a simpler and significantly more cost-effective approach has been introduced through “integral coherent measurements” because they yield an integral of the signal response over the entire length of the optical fibre sensor. This sensing system proves to be suitable to provide an overall indication of the state of the entire monitored domain and yield indications of the onset of motion with a high temporal resolution. The sensor has been tested in controlled conditions as a monitoring tool in a downscaled landslide model. We exploit the large bandwidth and high frequency of acquisition in order to detect high frequency elastic waves. The proposed sensor is able to distinguish the vibration footprint generated by ground movement. The results obtained from the experimental tests demonstrate that the proposed sensing system is able to recognize the onset of motion some minutes before a visual indication of instability could be observed
An objective Bayesian analysis of dichotomous sensitive data
No full textWe consider a dichotomous population in which every
person belongs either to a sensitive group or to the non
sensitive complement . The object of interest is to
estimate the population proportion of individuals who are members
of . We refer to a randomized response model proposed by Huang
(2004), where also another parameter is present, namely the
probability that a respondent truthfully states that he/she
belongs to in a direct response survey. In the paper the
posterior distribution of the parameters under the joint Jeffreys
and Reference prior is derived. The properties of the
noninformative priors are investigated through the frequentist
coverage probabilities of posterior quantiles
Models in SAE when covariates are measured with error
No full textIn this chapter we will discuss some issues related to the use of covariates measured with error in a small area statistical model.We will present a review of the existing literature, both from a frequentist and a Bayesian perspective.We will also discuss some new methodological issues and illustrate the methods through a real data application
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