Exfo Electro-Optical Engineering, Inc.

Expo Electro- Optical Engineering Inc.

Normand Cyr

Fran&ccedil;ois Babin

An interferometric optical analyzer apparatus comprises a light source, an interferometer and a detection system for determining the linear response, and subsequently any optical parameter, of one or more optical elements using substantially unpolarized light. In one embodiment, the light source supplies substantially unpolarized coherent light over a predetermined range of optical frequencies. The optical element is coupled in one arm of the interferometer and the other arm of the interferometer is used as a reference. The unpolarized light is first passed through the interferometer then through a three-way polarization splitter unit to split the light into at least three light beams according to preselected polarization axes corresponding to three linearly independent states of polarization. The three light beams are coupled to individual detectors and a controller computes Jones matrix elements from the resulting electrical signals. The total polarization independent power may also be determined by an additional detector.

Interferometric optical analyzer and method for measuring the linear response of an optical component

Apparatus for measuring polarization mode dispersion (PMD) of a device, e.g. a waveguide, comprises a broadband light source () for passing polarized broadband light through the device (), an interferometer () for dividing and recombining light that has passed through the device to form interferograms, a polarization separator () for receiving the light from the interferometer and separating such received light along first and second orthogonal Feb. 25, 2003 Feb. 25, 2003 polarization states, detectors () for converting the first and second orthogonal polarization states, respectively, into corresponding first and second electrical signals (P(&#x3c4;),P(&#x3c4;)), and a processor () for computing the modulus of the difference and such, respectively, of the first and second electrical signals to produce a cross-correlation envelope (E(&#x3c4;)) and an auto-correlation envelope (E(&#x3c4;)), and determining the polarization mode dispersion according to the expression PMD=where and &#x3c4; is the delay difference between the paths of the interferometer.

Method and apparatus for measuring polarization mode dispersion

A property of a device that is dependent upon both wavelength and state of polarization is measured by; passing through the device an optical signal having its wavelength and SOP varied, the wavelength over a spectral range of the device and the SOP between four Mueller SOPs; measuring the insertion loss of the device for each of the four SOPS and at each wavelength; using the four insertion loss measurements for each of the four different states of polarization for each wavelength to compute the four elements of the first line of the Mueller matrix for each wavelength; and using the Mueller matrix elements, computing insertion loss variations for the device for a multiplicity of input states of polarization in addition to the four states of polarization for which the actual attenuation measurements were made and using the insertion loss variations to compute the polarization and wavelength dependent property.

Measurement of optical properties of passive optical devices using the matrix method

In order to avoid errors inherent in the measurement of electrical phase differences or pulse arrival time in relative group delay measurements, different optical signals have their intensity modulated at a common high frequency and different permutations are selected. The amplitudes of corresponding electrical signals are detected and phase differences are computed on the basis of trigonometrical relationships. Because the modulation frequency is known, time differences can be deduced. Apparatus for measuring the phase differences conveniently comprises a slotted wheel ( ) which passes selected ones or both of the optical signals. One of the optical signals may be split to produce a third signal with a predetermined phase shift, e.g. about 90 degrees at the modulation frequency and the amplitudes of some possible permutations of the three optical signals used to compute the phase difference. The measurements may be used to compute chromatic dispersion, polarization mode dispersion, elongation, and so on.

Method and apparatus for measuring phase differences between intensity-modulated optical signals

Apparatus for measuring very low levels of polarization mode dispersion of optical devices, that is inexpensive, robust and portable, comprises a broadband source and a polarizer for directing substantially completely polarized broadband light into the device under test with the polarization in a plane substantially perpendicular to the propagation direction of the light. Light leaving the device is analyzed spectrally to produce a spectrum of intensity in dependence upon wavelength or frequency of such light for each of at least two mutually orthogonal polarization axes in a plane perpendicular to the propagation axis of the light leaving the device. The spectra are used to compute Stokes parameters s,, s,and &verbar;s,&verbar; for each of a plurality of wavelengths within the bandwidth of the broadband light. The polarization mode dispersion of the device is characterized in dependence upon the Stokes parameters using one of several techniques including standard Fixed Analyzer techniques and polarimetric techniques, especially the Poincar&eacute; sphere technique. The apparatus is particularly suitable for measuring PMD of components of optical telecommunications systems, including optical fibers, optical isolators, couplers, light amplifiers, and dispersion compensators.

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Sainte-Foy, Canada

Normand Cyr