Patent ID: 7444082
Filing Date: 2008-10-28
Classification: G02B,H04B

Abstract:
1. Method for the adaptive adjustment of a PMD compensator in optical fiber communication systems with the compensator comprising a cascade of adjustable optical devices over which passes an optical signal to be compensated comprising the steps of: a. extracting the y b. obtaining the signal y(t)=|y c. sampling the signal y(t) at instants t d. computing the mean square value of the error e(k)=y(t e. producing control signals for parameters of at least some of said adjustable optical devices to tend toward minimization of the mean square value of e(k), in which said parameters being consolidated in a vector θ and a function F(θ)=e(k) being defined the parameters are adjusted to tend to minimize the mean value of F in which the vector θ of the parameters is updated by adding a new vector with the norm proportionate to the norm of the gradient of F so that movement is towards a relative minimum of the function F in which in the error F(θ)=e(k) the transmitted information symbol u(nL) is substituted with the corresponding decision û(nL) so as to substitute the error e(k) with the estimated error ê(k) defined as ê(k)=y(t in which G[θ(nL)]=E{ê and in which the partial derivatives of G(θ) for θ=θ(t Step 1. Find the value of G[θ(nL)]=G[φ Step 2. Find the partial derivative: at iteration n; to do this, parameter φ 1 is set at φ 1 (nL)+Δ while the other parameters are left unchanged; the corresponding value of G(θ), G[φ 1 (nL)+Δ,φ 2 (nL), θ 1 (nL), θ 2 (nL)] is computed as in step 1 but in the time interval (nLT+LT/5, nLT+2LT/5); the estimate of the partial derivative of G(θ) with respect to φ 1 is computed as: Step 3. Find the partial derivative: at iteration n; to do this the parameter φ 2 is set at φ 2 (nL)+Δ while the other parameters are left unchanged; the corresponding value of G(θ), G[φ 1 (nL), φ 2 (nL)+Δ,θ 1 (nL), θ 2 (nL)], is computed as in step 1 but in the time interval (nLT+2LT/5, nLT+3LT/5); the estimate of the partial derivative of G(θ) with respect to φ 2 is computed as: Step 4. Find the partial derivative: at iteration n; to do this, parameter θ 1 is set at θ 1 (nL)+Δ while the other parameters are left unchanged; the corresponding value of G(θ), G[φ 1 (nL),φ 2 (nL), θ 1 (nL)+Δ,θ 2 (nL)], is computed as in Step 1 but in the time interval (nLT+3LT/5, nLT=4LT/5); the estimate of the partial derivative of G(θ) with respect to θ 1 is computed as: Step 5. Find the partial derivative: at iteration n; to do this the parameter θ 2 is set at θ 2 (nL)+Δ while the other parameters are left unchanged; the corresponding value of G(θ), G[φ 1 (nL),φ 2 (nL),θ 1 (nL),θ 2 (nL)+Δ], is computed as in Step 1 but in the time interval (nLT+4LT/5, (n+1)LT); the estimate of the partial derivative of G(θ) with respect to θ 2 is computed as: