1.
Viberg, Mats, 1961, et al.
(author)
Maximum Likelihood Array Processing in Spatially Correlated Noise Fields Using Parameterized Signals
1997
In: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1941-0476 .- 1053-587X. ; 45, s. 996-1004
Journal article (peer-reviewed) abstract
This paper deals with the problem of estimating signal parameters using an array of sensors. This problem is of interest in a variety of applications, such as radar and sonar source localization. A vast number of estimation techniques have been proposed in the literature during the past two decades. Most of these can deliver consistent estimates only if the covariance matrix of the background noise is known. In many applications, the aforementioned assumption is unrealistic. Recently, a number of contributions have addressed the problem of signal parameter estimation in unknown noise environments based on various assumptions on the noise. Herein, a different approach is taken. We assume instead that the signals are partially known. The received signals are modeled as linear combinations of certain known basis functions. The exact maximum likelihood (ML) estimator for the problem at hand is derived, as well as a computationally more attractive approximation. The Cramer Rao lower bound (CRB) on the estimation error variance is also derived and found to coincide with the CRB, assuming an arbitrary deterministic model and known noise covariance.
2.
Anders, Berntson, et al.
(author)
Self-phase modulation in dispersion compensated optical fibre transmission systems
1996
In: Optics Communications. - : Elsevier. - 0030-4018 .- 1873-0310. ; 130:1-3, s. 153-162
Journal article (peer-reviewed) abstract
An analysis is made of the influence of self-phase modulation on optical fibre communication systems where the chromatic dispersion is compensated for by a dispersion compensation fibre. In particular we derive a simple and useful expression for the optimal fibre length in the presence of nonlinearities.
3.
Bakhshi, Bamdad, 1970, et al.
(author)
Measurement of the differential group delay in installed optical fibers using polarization multiplexed solitons
1999
In: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 11:5, s. 593-595
Journal article (peer-reviewed) abstract
We experimentally demonstrate a new technique for measurement of the differential group delay (DGD) in optical fibers using polarization-division multiplexed (PDM) solitons: the change in the separation of orthogonally polarized solitons propagating along different principal axes in a fiber equals the DGD at the signal wavelength. Based on this principle, we use PDM solitons to measure the accumulated DGD at different distances along a 400-km installed fiber. The measured DGD exhibits the expected square-root-of-length dependence, corresponding to a polarization-mode dispersion of 0.26 ps/km1/2. The results are in excellent agreement with those obtained by a commercial instrument utilizing Jones matrix eigenanalysis.
4.
Bakhshi, Bamdad, 1970, et al.
(author)
Soliton interaction penalty reduction by receiver filtering
1998
In: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 10:7, s. 1042-1044
Journal article (peer-reviewed) abstract
We present the first detailed numerical study of the impact of receiver low-pass filtering in soliton interaction-limited communication systems. We propagate 40-Gb/s pseudorandom bit sequences (PRBS's) of 28-1 solitons up to one soliton collision distance (Zc-) and optimize the filter bandwidth to minimize the interaction induced eye opening penalty. The distance at 0.5-dB penalty is increased over 40% through filtering. The penalty is essentially pulsewidth independent when considering distances normalized by Zc. We also show that PRBS's of at least 28 - 1 solitons are required to accurately simulate random data.
5.
Hedekvist, Per Olof E, 1967, et al.
(author)
Polarization dependence and efficiency in a fiber four-wave mixing phase conjugator with orthogonal pump waves
1996
In: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 8:6, s. 776-778
Journal article (peer-reviewed) abstract
We study the influence of pump separation on polarization dependence and on conversion efficiency in a fiberbased optical phase-conjugator with two orthogonal pump waves at different wavelengths. The polarization dependence is found to be minimized when the pump wavelength separation is small. Furthermore, both theory and experiments show that the efficiency is maximized if the signal wavelength is located close to one of the pumps.
6.
Karlsson, Magnus, 1967, et al.
(author)
Autocorrelation function of the polarization-mode dispersion vector
1999
In: Optics Letters. - 0146-9592 .- 1539-4794. ; 24:14, s. 939-941
Journal article (peer-reviewed) abstract
We derive, for what is believed to be the first time, the autocorrelation function (ACF) of the polarization-mode dispersion (PMD) vector, which gives information on the bandwidths of the principal states of polarization. We compare the ACF with measured data and find good agreement. Finally, we apply the derived ACF to calculate the average pulse broadening that is due to PMD.
7.
Karlsson, Magnus, 1967
(author)
Polarization mode dispersion induced pulse broadening in optical fibers
1998
In: Optics Letters. - 0146-9592 .- 1539-4794. ; 23:9, s. 688-690
Journal article (peer-reviewed) abstract
A simple and exact analytical expression is derived for the amount of broadening that a pulse suffers when it is subjected to the combined actions of polarization mode dispersion, chromatic dispersion, and chirping. The theory is then applied to various manifestations of second-order polarization mode dispersions.
8.
Olsson, Bengt-Erik, 1968, et al.
(author)
Polarization mode dispersion measurement using a Sagnac interferometer and a comparison with the fixed analyzer method
1998
In: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 10:7, s. 997-999
Journal article (peer-reviewed) abstract
Polarization mode dispersion measurement using a Sagnac interferometer is compared with the well-known fixed analyzer technique both theoretically and experimentally. It is shown that in the case of weak mode coupling in the fiber the Sagnac interferometer method is equivalent to the fixed analyzer method but gives better readability of the measured optical spectrum. For strong mode coupling, we develop a theory that relates the differential group delay to the number of mean-level crossings in the measured spectrum.
9.
Zhang, Xiupu, et al.
(author)
Design guidelines of actively mode-locked fiber ring lasers
1998
In: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 10:8, s. 1103-1105
Journal article (peer-reviewed) abstract
This letter presents guidelines of how to design actively mode-locked fiber ring lasers to generate nearly transform-limited soliton pulses. The minimum fiber cavity length and/or dispersion, with which nearly transform-limited soliton pulses can be generated, need to satisfy an additional condition besides two previously known conditions of stability.
10.
Zhang, Xiupu, et al.
(author)
Polarization-division multiplexed solitons in optical fibers with polarization-mode dispersion
1998
In: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 10:12, s. 1742-1744
Journal article (peer-reviewed) abstract
We point out that the use of polarization-division multiplexed solitons is only preferable to a copolarized pulse train only if the system is interaction-limited and the polarization-mode dispersion (PMD) is sufficiently weak. If the PMD is stronger, copolarized solitons perform better than polarization-division multiplexed ones. A simple analytical formula for when this occurs is derived.
