1,721,038 research outputs found
Gain dynamics in doped-fiber amplifiers for added and dropped signals
No full textSun e2 al. [l] reduced the set of coupled iirst
order nonlinear partial differential equations determining
the wavelength-dependent, time-varying doped-fiber amplifier
gain into a single ordinary differential equation (ODE).
In this paper we further simplify the ODE, greatly enhancing
its utility as an analysis and design tool. We find that
the gain dynamics are completely specified by the total
number of excited ions. We demonstrate that channel addition
causes much faster transients than channel dropping
in wavelength division multiplexing networks. We approximate
the solution of the ODE by an exponential with time
constant given as a function of amplifier parameters
Large power swings in doped-fiber amplifiers with highly variable data
No full textWe show that doped-fiber amplifiers operated in
saturation can display very fast transient dynamics and large
power swings in a packet switching environment with highly
variable packet interarrival times
Simple dynamic model of fibre amplifiers andequivalent electric circuit
No full textBuilding on the results in [l], the authors have determined that
the gain dynamics of a doped-fibre amplifer are completely
specified by its total number of excited ions whose time behaviour
is described by a simple first-order differential equation. An
equivalent electrical circuit is derived, so that any circuit analysis
package can be used to solve for complex networks of optical
fibre amplifiers
Large power and SNR swings in cascaded EDFAs carrying highly variable traffic
No full textWe show that cascades of EDFAs carrying packetized trafic with high vuriability can display large outpur
power and SNR swings due to the gain saturation effect
Output power and SNR swings in cascades of EDFAs for circuit- and packet-switching optical networks
No full textA simple dynamic model of the erbium-doped fiber
amplifier (EDFA) that includes self-saturation by amplified spontaneous
emission (ASE) is used to analyze the power and signalto-
noise ratio (SNR) transients in wavelength division multiplexed
(WDM) optical networks in which signals cross chains of EDFA’s
from source to destination. The model, which consists of solving
sequentially one ordinary differential equation per amplifier, is
used to 1) determine power and SNR excursions in the surviving
channels along a chain of 35 EDFA’s during isolated add–drop
events in a 16-channel WDM circuit switching scenario and 2)
run Monte Carlo simulations of the first five EDFA’s of the
same chain fed by burst-mode packet switching traffic on each of
the 16 channels. Each packet source is modeled as an ON–OFF
asynchronous transfer mode (ATM) source, with ON and OFF
times having a heavy-tailed Pareto distribution. The aggregate
source model is asymptotically self-similar, and well describes
multimedia packet communications. The results are used to
examine the influence of average network utilization and source
ON–OFF time variance on the probability density function of signal
power and SNR at each EDFA output. We demonstrate that selfsimilar
traffic generates sizable power and SNR swings, especially
at low network utilization. The simulations also indicate sizable
broadening of the power and SNR density functions along the
cascade of EDFA’s, reaching levels in excess of 9 dBm and 4 dB
for the power and SNR swings, respectively, at the 5th EDFA.
The effect becomes more pronounced for longer EDFA chains.
Such a large broadening may imply serious system impairments
in burst-mode WDM packet networks
Fast dynamics and power swings in doped-fiber amplifiers fed by highly variable multimedia traffic
No full textErbium-doped fiber amplifier (EDFA) transient gain dynamics in
wavelength-division multiplexing (WDM) transmission systems for circuit-
switching applications have recently been shown to be rather slow,
in the range oftens to hundreds of ps.’ We show here that such dynamics
can be much faster, and give rise to large power swings, in a packetswitching
environment with highly variable packet interarrival times,
such as with self-similar traffic
Gain control in EDFA's by pump compensation
No full textGain control by means of pump compensation in
cascades of erbium-doped fiber amplifiers (EDFA’s) is analyzed.
Based on analytical expressions for the 1-dB rise/fall time for the
case of channels add/drop, required pump power changes at each
amplifier are derived in the form of simple closed expressions.
Numerical simulations of a system comprising 20 wavelengthdivision-
multiplexed channels transmitted through a cascade of
35 EDFA’s are performed demonstrating the effectiveness of the
gain control
DQPSK: when is a narrow filter receiver is good enough?
No full textIn this paper, we investigate experimentally and via
simulation the pros and cons of a narrow filter receiver for differential
quadrature phase-shift keying based on a single optical filter
and eschewing the conventional asymmetrical Mach–Zehnder interferometer
structure. We quantify the performance differences
between the two receivers, allowing system designers and operators
to determine when the less complex narrow filter receiver
might be the appropriate choice.We numerically optimize the 3-dB
bandwidth and center frequency of the narrow filter and show
it is more robust to carrier frequency detuning than the conventional
solution. We show that the narrow filter receiver is more
tolerant to chromatic dispersion (CD) than the conventional one,
and equally tolerant to first-order polarization-mode dispersion.
We show the impact of the 3-dB bandwidth on the receiver performance
when CD accumulates. Finally, we show via experiments
and simulations that the 3 dB advantage of the conventional receiver
vanishes when the nonlinear impairments are fiber nonlinearities;
comparing the two receivers at the optimum launch power
for a 25x80 km system, the difference in optical SNR margin is
reduced to 1.6 dB. Experiments are conducted at 42 Gb/s using
a commercially available narrow filter for reception
Low Complexity Compensation of SOA Nonlinearity for Single-Channel PSK and OOK
No full textCarrier density fluctuations in semiconductor optical
amplifiers (SOAs) impose penalties on phase-shift keying (PSK)
signals due to nonlinear phase noise (NLPN), and on-off keying
(OOK) signals due to self-gain modulation. In this paper, we propose
a simple scheme to equalize the impairments induced by SOA
nonlinearities, derived from the small signal analysis of carrier
density fluctuations. We demonstrate via simulation almost complete
cancelation of the NLPN added by a saturated SOA on a
differential PSK signal. We demonstrate via both simulations and
experiment the effectiveness of the method for mitigation of nonlinear
distortions imposed by SOAs on an OOK signal
Multicanonical Monte Carlo for Simulation of Optical Links
No full textMulticanonical Monte Carlo (MMC) is a simulation-acceleration technique for the estimation of the statistical distribution of a desired system output variable, given the known distribution of the system input variables. MMC, similarly to the powerful and well-studied method of importance sampling (IS) [1], is a useful method to efficiently simulate events occurring with probabilities smaller than ~ 10^ − 6, such as bit error rate (BER) and system outage probability. Modern telecommunications systems often employ forward error correcting (FEC) codes that allow pre-decoded channel error rates higher than 10 ^− 3; these systems are well served by traditional Monte-Carlo error counting. MMC and IS are, nonetheless, fundamental tools to both understand the statistics of the decision variable (as well as of any physical parameter of interest) and to validate any analytical or semianalytical BER calculation model. Several examples of such use will be provided in this chapter. As a case in point, outage probabilities are routinely below 10^ − 6, a sweet spot where MMC and IS provide the most efficient (sometimes the only) solution to estimate outages
- …
