Exfo Electro-optical Engineering, Inc.

Fran&ccedil;ois Babin

Normand Cyr

Gang He

Gregory Walter Schinn

Steeve Potvin

Martin Tremblay

Marc Breton

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

A photodetector device comprising a photosensitive detector ( ) and one or more interfaces ( ) between dissimilar media is configured so that a light beam (LB) for detection will pass through the interface(s) along a beam axis that is not normal to the interface(s). The deviation (&thgr;) from the normal will be such that polarization dependent transmission introduced at the interface(s) will compensate for inherent polarization dependency of the detector ( ). The deviation may be achieved by inclining the interface(s) relative to a predetermined direction along which the light beam will be incident. Where the photosensitive detector is in a housing ( ) with a window ( ) through which the light beam enters the housing, the housing can be tilted. In such as case, there are three interfaces, one ( ) at the surface of the detector ( ), and one at each surface ( ) of the window ( ). Alternatively, the detector surface and/or the window could be tilted. Where a pigtail fiber ( ) is permanently attached to the photodetector device to input the light beam through an interposed lens ( ), the end of the pigtail fiber may be offset laterally from the lens optical axis (LOA) so that the beam axis deviates from the normal by such an angle that the resulting polarization dependent transmission (PDT) substantially corrects for polarization dependent response (PDR) of the photosensitive detector. An end facet of the pigtail fiber, the lens, and/or the window may be inclined so that they are not perpendicular to the propagation direction of the light beam so as to reduce interference and backreflection effects.

Polarization independent photodetector device and method of making same

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.

Growing community of inventors

Charlesbourg, Canada

François Babin

Growing community of inventors

Charlesbourg, Canada

Fran&ccedil;ois Babin

François Babin