US 11,644,381 B2 · Polarization dependent loss measurement

Abstract

There is provided a method for measuring the PDL of a DUT as a function of the optical frequency ν within a spectral range, which uses a single wavelength scan over which the input-SOP varies in a continuous manner. The power transmission through the DUT, curve T(ν), is measured during the scan and the PDL is derived from the sideband components of the power transmission curve T(ν) that results from the continuously varying input-SOP. More specifically, the Discrete Fourier Transform (DFT) of the power transmission curve T(ν) is calculated, wherein the DFT shows at least two sidebands. At least two sidebands are extracted and their inverse DFT calculated individually to obtain complex transmissions (ν), =−J . . . J, where J is the number of sidebands on one side. The response vector |m(ν) of the DUT is derived from the complex transmissions (ν) and a matrix determined by the continuous trajectory of the SOP of the input test lightwave; and the PDL of the DUT as a function of ν (PDL curve) is derived therefrom.

Claims19

Dependent claims

A method for measuring the Polarization Dependent Loss (PDL) of a Device Under Test (DUT) within a spectral range, comprising:

generating an input test lightwave which State Of Polarization (SOP), as represented by a point on the surface of the Poincaré sphere, varies according to a continuous trajectory while being spectrally scanned over the spectral range and launching the input test lightwave into the DUT;
measuring the power transmission through the DUT, curve T(ν), during a spectral scan of the input test lightwave;
calculating a Discrete Fourier Transform (DFT) of the power transmission curve T(ν), wherein the DFT shows at least two sidebands;
extracting said sidebands and computing an inverse DFT of each said sidebands to obtain complex transmissions (ν);
computing the response vector |m(ν) of the DUT from said complex transmissions (ν) and a matrix determined by the continuous trajectory of the SOP of the input test lightwave by solving the linear system of equations defined by |(ν)=|m(ν) wherein |(ν) is constructed from said complex transmissions (ν);
deriving the spectrally-varying PDL of the DUT from said response vector |m(ν).

3 more elements

A system for measuring the Polarization Dependent Loss (PDL) of a Device Under Test (DUT) within a spectral range, comprising:

a tunable light source to generate a test lightwave and spectrally scanning the test lightwave over the spectral range;
a State Of Polarization (SOP) generator connected to the tunable light source and configured for varying the SOP of the test lightwave according to a continuous trajectory on the surface of the Poincaré Sphere while the test lightwave is spectrally scanned over the spectral range, the test lightwave to be launched into the DUT;
a power transmission measurement apparatus connected to the SOP generator and comprising a first photodetector and a second photodetector for measuring power values of the test lightwave at the input and the output of the DUT, respectively;
an acquisition device connected to the power transmission measurement apparatus and comprising an analog-to-digital converter sampling the measured power values during a spectral scan of the test lightwave to produce a measured power transmission curve T(ν);
a processing unit connected to the acquisition device to receive said measured power transmission curve T(ν) and configured for:
calculating a Discrete Fourier Transform (DFT) of said power transmission curve T(ν), wherein the DFT shows at least two sidebands;
extracting said sidebands and computing an inverse DFT of each said sidebands to obtain complex transmissions (νv);
computing the response vector |m(ν) of the DUT from said complex transmissions (ν) and a matrix determined by the continuous trajectory of the SOP of the input test lightwave by solving the linear system of equations defined by |(ν)=|m(ν) wherein |(ν) is constructed from said complex transmission (ν);
and
deriving the spectrally-varying PDL of the DUT from said response vector |m(ν).

7 more elements

Dependencies are inferred from the claim text.

Polarization dependent loss measurement

Life of this patent

Polarization dependent loss measurement

Life of this patent

Abstract

Claims19