Press Releases
12 May 2003
Circadiant Releases White Paper on Statistical Uncertainty of BER Measurements
Optical Standards Tester is first to integrate automated
physical layer measurements with statistical analysis.
Allentown PA - Circadiant Systems, Inc., the company making optical
testing simple, today released a white
paper that explains the relationship between Bit Error
Ratio (BER) measurements and their statistical confidence levels.
Circadiant Optical Standards Testers (OSTs) include BER statistical
analysis, with continuously updated confidence levels.
Often there is a trade-off between the time spent
on a test and the certainty of the BER measurement. When the BER
is low, a test needs to run for a long period before many errors
occur. Yet when a BER test is repeated again and again, a range
of different results is expected. Therefore, a statistical uncertainty
must be associated with any BER measurement. In the past, it has
been necessary to calculate this uncertainty manually. Now, sophisticated
algorithms continuously provide OST users with graphical BER statistical
confidence levels of each data point taken in automated physical
layer measurements such as sensitivity, overload, BER vs. OSNR,
and 10 Gigabit Ethernet stressed receiver conformance.
In the Circadiant white paper, “Statistical
Uncertainty of BER Measurements,” various statistical analyses
of BER measurements are described. These include binomial probability,
Poisson approximation, cumulative Poisson distributions, Gaussian
probability distributions, one-sided and two-sided confidence levels,
high error cases, no error cases, and Circadiant’s plotting
conventions.
“Associated with a BER value is a confidence
level and an input condition, such as the optical power level,” said
Joey Thompson, Circadiant’s CTO. “For example, one
could say a BER is not greater than 10 to the –12, with a
95% confidence level, at –19.33 dBm.” An OST also employs
advanced algorithms that utilize the data points, and their associated
confidence levels, to calculate the sensitivity of a Device Under
Test. The OST will also extrapolate the sensitivity to low BER
values such as 10 to the -14.
The Circadiant web site also includes a series of
technical briefs. “BER vs. OSNR” explains how BER measurements
may be performed as a function of OSNR rather than optical power. “Sensitivity
Measurement Algorithms” reveals a variety of modes an OST
applies to automatically measure sensitivity. “Straight-Line
BER Plots” describes how to plot BER results so they easily
reveal abnormal receiver behavior. And the “Optical Signal
to Noise Ratio (OSNR)” technical brief offers a detailed
approach to accurate OSNR measurements.
About OSTs
OSTs are an important new
class of test instrumentation. They have received
numerous awards as innovative test instruments
that reduce manufacturing test cycle times and
shorten a new product's time-to-market. Components
and instruments that measure layer 1, 2 and 3
that are commonly used to test optical communication
systems are consolidated into an OST. This enables
sophisticated algorithms and complex testing
procedures to be calibrated and automated by
Circadiant, instead of the user, and produces
a test instrument that is fast, accurate and
purpose-built for optical communication system
testing. Individual and group test results are
displayed on appropriate scales with statistical
confidence levels clearly shown to help users
understand the behavior of a Device Under Test.
An OST also allows the user to degrade test signals
to simulate worst-case operating conditions.
Degradation includes control over jitter, OSNR,
interfering source, extinction ratio and optical
power as well as the ability to inject errors
into the layer 2 and 3 protocol signals.
About Circadiant Systems, Inc.
Led by test industry veterans and staffed by a team of distinguished physicists
and engineers, Circadiant is a privately-held company based in Allentown, PA.
The company provides optical component developers, network equipment manufacturers,
and telecom service providers with award-winning test systems. Circadiant’s
Optical Standards Testers generate real-world optical test signals that greatly
improve network reliability and interoperability. Circadiant received venture
funding from EnerTech Capital, Intel Capital, PA Early Stage, and TL Ventures.
Media Contacts:
John French
Circadiant Systems, Inc.
610.871.0500 x101
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