Ericsson Ab

Telefonaktiebolaget Lm Ericsson (publ)

Marconi Communications Gmbh

Giancarlo Prati

Enrico Forestieri

Giulio Colavolpe

Marco Secondini

Tommaso Foggi

A method of and a receiver() for detection of a received signal in an optical fiber communication system using Viterbi algorithm methodology in which branch metrics are obtained using approximated expressions to calculate the branch metrics. Use of the expressions results in practically the same performance as a receiver based on exact metrics.

Maximum likelihood sequence estimation in optical fibre communication systems

A polarization multiplex transmission system () comprises two optical signals (z, z) transmitted over the same optical fiber () at the same wavelength but with orthogonal polarizations. The system is characterized by receiving apparatus () which is operable to filter the two components with orthogonal polarization of the signal received in accordance with an appropriate transfer matrix which is dynamically controlled on the basis of the output signals in such a manner as to approximate the reverse transfer matrix of the fiber in the region of the spectrum occupied by the signal so as to compensate for Polarization Mode Dispersion (PMD) and polarization rotation introduced by the fiber and eliminating distortion and mutual interference effects for both the signals and thereby obtain a demultiplexed output corresponding to the two transmitted signals.

System, method and apparatus for polarization mode dispension compensation and demultiplexing polarization multiplexed signals

A method for the adaptive adjustment of a PMD compensator in optical fiber communication systems comprises the steps of taking the signal at the compensator output and extracting the components y(t) and y(t) on the two orthogonal polarizations, computing the signal y(t)=[y(t)]+[y(t)], sampling the signal y(t) at instants t=kT with T=symbol interval to obtain samples y(t), computing the mean square error e(k)=y(t)&#x2212;u(k) with u(k) equal to the symbol transmitted, and adjusting the parameters of the compensator to seek to minimize e(k). A PMD compensator in accordance with the method comprises an adjustment system which comprises in turn a photodetecor () which takes the components y(t) and y(t) on the two orthogonal polarizations from the signal at the compensator output, a sampler () which samples at instants t=kT with T=symbol interval, the signal y(t)=[y(t)]+[y(t)]at the output of the photodetector () to obtain samples y(t), a circuit () for computation of the mean square error e(k)=y(t)&#x2212;u(k) with u(k) equal to the symbol transmitted, and a regulator () which regulates the parameters of the compensator to seek to minimize e(k).

Polarisation mode dispersion compensator using a mean square error technique

A coding scheme of order n for digital communications, in particular optical communication, for obtaining a coded signal x(t) which represents binary data which are constituted by sequences of information bits {u} with rate T, the scheme having N=2states, named &#x3a3;, for i=1, 2, . . . , N, and comprising predetermined elementary signals s(t) which are combined in the signal x(t). According to the scheme, if, at the time t=kT, the coding is in a state &#x3a3;of the N states, the arrival of the information bit uof the sequence {u} forces a transition to the state &#x3a3;of the N states and the selection of the elementary signal s(t) as x(t), where q and i are given by the following equations: d=m&#x2212;1 mod 2; d=d+umod 2; y=2(m&#x2212;1)+d; q=(r mod N)+1; and i=r+1 if r&#x3c;N, or i=r&#x2212;2N otherwise.

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Parma, Italy

Giancarlo Prati