An optimization method for the decision threshold level in optical receivers for WDM-PONs

2006 ◽  
Author(s):  
Sil-Gu Mun ◽  
Chang-Hee Lee
Keyword(s):  
Threshold Level ◽  
Optimization Method ◽  
Decision Threshold ◽  
Optical Receivers

Non-Adaptive Decision Thresholds for Gain Saturated FSO Links Limited by Weak to Strong Turbulence and Pointing Errors

2020 ◽  
Vol 46 ◽  
pp. 63-75
Author(s):  
Jeremiah Oluwatosin Bandele ◽  
Moses Oluwafemi Onibonoje ◽  
Abisayo O. Aladeloba
Keyword(s):  
Atmospheric Turbulence ◽  
Communication Systems ◽  
Threshold Level ◽  
High Gain ◽  
Decision Threshold ◽  
Free Space Optical ◽  
Pointing Errors ◽  
Strong Turbulence ◽  
Simulation Techniques ◽  
Amplified Spontaneous Emission Noise

In free space optical (FSO) communication systems limited by atmospheric turbulence, the use of non-adaptive decision thresholds to determine the transmitted bits results in bit error rate (BER) floors at high BER values in all turbulence regimes. Practically implementing an adaptive decision threshold that can properly track the fluctuations due to atmospheric turbulence is challenging, therefore, devising ways of optimising the non-adaptive decision threshold used by FSO designers is necessary. In this paper, the investigation of gain saturated pre-amplified FSO communication systems using non-adaptive decision thresholds in the presence of atmospheric turbulence, pointing errors (PEs), geometric spread (GS) and amplified spontaneous emission noise is carried out by applying analytical methods and Monte Carlo (MC) simulation techniques. System performance is carried out for various turbulence regimes, normalised beam widths, normalised PE standard deviations and small signal gains using fixed gain and gain saturated optical amplifiers (OAs). Results obtained show that in the presence of atmospheric turbulence, PE and GS, optimal BER performances are obtained with OA input powers higher than the internal saturation power of the OA. Also, by using high gain OAs and varying the decision threshold level, acceptable BER performances can be obtained in strong turbulence regimes with a non-adaptive decision threshold.

scholarly journals When expectations are not met: unraveling the computational mechanisms underlying the effect of expectation on perceptual thresholds

2019 ◽  
Author(s):  
Buse M. Urgen ◽  
Huseyin Boyaci
Keyword(s):  
Visual Processing ◽  
Prior Information ◽  
Spatial Location ◽  
Threshold Level ◽  
Behavioral Effects ◽  
Decision Threshold ◽  
Internal Parameters ◽  
Speed Up ◽  
Task Irrelevant ◽  
Violation Of Expectation

AbstractExpectations and prior knowledge strongly affect and even shape our visual perception. Specifically, valid expectations speed up perceptual decisions, and determine what we see in a noisy stimulus. Bayesian models have been remarkably successful to capture the behavioral effects of expectation. On the other hand several more mechanistic neural models have also been put forward, which will be referred as “predictive computation models” here. Both Bayesian and predictive computation models treat perception as a probabilistic inference process, and combine prior information and sensory input. Despite the well-established effects of expectation on recognition or decision-making, its effects on low-level visual processing, and the computational mechanisms underlying those effects remain elusive. Here we investigate how expectations affect early visual processing at the threshold level. Specifically, we measured temporal thresholds (shortest duration of presentation to achieve a certain success level) for detecting the spatial location of an intact image, which could be either a house or a face image. Task-irrelevant cues provided prior information, thus forming an expectation, about the category of the upcoming intact image. The validity of the cue was set to 100, 75 and 50% in different experimental sessions. In a separate session the cue was neutral and provided no information about the category of the upcoming intact image. Our behavioral results showed that valid expectations do not reduce temporal thresholds, rather violation of expectation increases the thresholds specifically when the expectation validity is high. Next, we implemented a recursive Bayesian model, in which the prior is first set using the validity of the specific experimental condition, but in subsequent iterations it is updated using the posterior of the previous iteration. Simulations using the model showed that the observed increase of the temporal thresholds in the unexpected trials is not due to a change in the internal parameters of the system (e.g. decision threshold or internal uncertainty). Rather, further processing is required for a successful detection when the expectation and actual input disagree. These results reveal some surprising behavioral effects of expectation at the threshold level, and show that a simple parsimonious computational model can successfully predict those effects.

Measurement of thyrotropin receptor antibodies (TRAK) with a second generation assay in patients with Graves’ disease

2000 ◽  
Vol 39 (04) ◽  
pp. 113-120 ◽  
Author(s):  
G. Wunderlich ◽  
R. Koch ◽  
W.-G. Franke ◽  
K. Zöphel
Keyword(s):  
Drug Treatment ◽  
Second Generation ◽  
Antithyroid Drug ◽  
Threshold Level ◽  
Optimal Decision ◽  
Graves Disease ◽  
Decision Threshold ◽  
Healthy Controls ◽  
Antithyroid Drug Treatment ◽  
Receptor Antibodies

Summary Aim: The detection of TSH-receptor-antibodies (TRAb) in patients (pts) with Graves’ disease (GD) is routinely used in nuclear medicine laboratories. It is performed by commercial, porcine radioreceptorassays (RRA) measuring TSH binding inhibitory activity. A second generation assay using the human, recombinant TSHreceptor was developed during the last years. The manufacturer composed this new assay as a coated tube RRA (CT RRA) and claimed a higher sensitivity for GD. Methods: TRAb was measured in 207 pts with various thyroid disorders and 205 healthy controls using the new coated tube RRA (Fa. B.R.A.H.M.S. Diagnostica GmbH, Berlin, Germany) as well as a conventional RRA (Fa. Medipan Diagnostica GmbH, Selchow, Germany): 60 pts suffering from GD showing a relapse after antithyroid drug treatment and before radioiodine therapy, 109 pts with disseminated autonomia (DA) and 38 pts suffering from Hashimoto’s thyroiditis. A ROC-analysis was performed to find the optimal decision threshold level for positivity. Results: We found 42/60 TRAbpositive pts with GD in the established RRA (threshold 6 U/L) and 52/60 in the CT RRA, respectively. The sensitivity increased from 70% (RRA) to 86,7% (CT RRA). The CT RRA found 2 false positives (one Hashimoto’s and one healthy control) and the RRA detected 3 Hashimoto’s and 2 healthy controls as false positive. Conclusion: The increased sensitivity of CT RRA for GD provides an advantage compared to conventional RRA, especially in GD-patients relapsing after antithyroid drug treatment. Functional sensitivity and Interassayvariation of CT RRA are very precisely compared to conventional RRA. Handling of the new assay is also improved.

Maternal DDAVP-induced hyponatremia: Threshold level for fetal urinary diuresis

1998 ◽  
Vol 5 (1) ◽  
pp. 151A-151A
Author(s):  
M NIJLAND ◽  
T ROBERTS ◽  
M CURRAN ◽  
M ROSS
Keyword(s):  
Threshold Level
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