Exfo Inc.

Exfo Optics, Sas

Normand Cyr

Bernard Ruchet

Gang He

Hongxin Chen

Daniel Gariepy

Gregory Walter Schinn

There is provided a method for measuring the PDL of a DUT as a function of the optical frequency &#x3bd; 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(&#x3bd;), is measured during the scan and the PDL is derived from the sideband components of the power transmission curve T(&#x3bd;) that results from the continuously varying input-SOP. More specifically, the Discrete Fourier Transform (DFT) of the power transmission curve T(&#x3bd;) 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(&#x3bd;),=&#x2212;J . . . J, where J is the number of sidebands on one side. The response vector |m(&#x3bd;)of the DUT is derived from the complex transmissions(&#x3bd;) and a matrixdetermined by the continuous trajectory of the SOP of the input test lightwave; and the PDL of the DUT as a function of &#x3bd; (PDL curve) is derived therefrom.

Polarization dependent loss measurement

Method and systems for characterizing an optical signal propagating along a communication link are disclosed. The signal includes a data-carrying signal contribution, modulated at a symbol frequency, and a noise contribution. The method includes measuring an optical power spectrum of the signal, which includes a data-carrying signal spectrum component and a noise spectrum component. The method also includes determining a measured spectral correlation function within pairs of spectral components of the signal as a function of center frequency of the pairs, the spectral components in each pair being spectrally separated from each other by the symbol frequency. The method further includes obtaining a solution for the data-carrying signal spectrum component based on the measured optical power spectrum, such that a calculated spectral correlation function based on the solution matches the measured spectral correlation function. In some embodiments, the spectral correlation function is measured as a low-frequency beatnote amplitude function.

Noise-free measurement of the spectral shape of a modulated signal using spectral correlation

A polarization-related characteristic of an optical path is determined from a predetermined function of the mean-square of a plurality of differences between polarization-analyzed optical power parameters corresponding to pairs of wavelengths mutually spaced about a midpoint wavelength by a small optical frequency difference. At least some of the said differences correspond to wavelength pairs measured under conditions where at least one of midpoint wavelength, input state of polarization (I-SOP) or analyzed state of polarization (A-SOP) of a pair is different.

Determining a polarization-related characteristic of an optical link

A portable inspection probe for the inspection of a recessed mating surface of an optical fiber connector is provided. In one variant, the portable inspection probe includes a digital holographic detection module operable to digitally record a hologram of the recessed mating surface, and a rigid probe tip configured to be optically coupled to the digital holographic detection module and shaped to provide optical access to the recessed mating surface. In another variant, the portable inspection probe is to be used with a rigid probe tip connectable thereto, and the digital holographic detection module includes a probing optical assembly not traversed by a reference beam and configured to direct an object beam onto the recessed mating surface and to collect the object beam upon reflection thereof by the recessed mating surface. An inspection system and an inspection method are also provided.

Portable digital holographic probe for the inspection of optical fiber connectors, and inspection system and method for the same

A portable apparatus for measuring optical powers of optical signals propagating concurrently in opposite directions in an optical transmission path between two elements, at least one of the elements being operative to transmit a first optical signal (S) only if it continues to receive a second optical signal (S) from the other of said elements, comprises first and second connector means for connecting the apparatus into the optical transmission path in series therewith, and propagating and measuring means connected between the first and second connector means for propagating at least the second optical signal (S) towards the one of the elements, and measuring the optical powers of the concurrently propagating optical signals (S, S). The measurement results may be displayed by a suitable display unit. Where one element transmits signals at two different wavelengths, the apparatus may separate parts of the corresponding optical signal portion according to wavelength and process them separately.

Method and apparatus for testing transmission lines normally propagating optical signals

A portable apparatus for measuring parameters of optical signals propagating concurrently in opposite directions in an optical transmission path between two elements, at least one of the elements being operative to transmit a first optical signal (S) only if it continues to receive a second optical signal (S) from the other of said elements, comprises first and second connector means for connecting the apparatus into the optical transmission path in series therewith, and propagating and measuring means connected between the first and second connector means for propagating at least the second optical signal (S) towards the one of the elements, and measuring the parameters of the concurrently propagating optical signals (S, S). The measurement results may be displayed by a suitable display unit. Where one element transmits signals at two different wavelengths, the apparatus may separate parts of the corresponding optical signal portion according to wavelength and process them separately.

Portable apparatus for measuring parameters of optical signals propagating concurrently in opposite directions in an optical transmission path between two elements, at least one of the elements being operative to transmit a first optical signal (S) only if it continues to receive a second optical signal (S) from the other () of said elements, comprises first and second connectors for connecting the apparatus into the optical transmission path in series therewith, and a device connected between the first and second connectors for propagating at least the second optical signal (S) towards the one of the elements, and measuring the parameters of the concurrently propagating optical signals (S, S). The measurement results may be displayed by a suitable display unit. Where one element transmits signals at two different wavelengths, the apparatus may separate parts of the corresponding optical signal portion according to wavelength and process them separately.

A method comprises: acquiring, for a number nSOP of varied State-Of-Polarization analysis conditions of the input optical signal, nSOP polarization-analyzed optical spectrum traces; mathematically discriminating said signal contribution from said noise contribution within said optical signal bandwidth using said polarization-analyzed optical spectrum traces, said mathematically discriminating comprising: obtaining a differential polarization response that is related to the optical spectrum of said signal contribution by a constant of proportionality; estimating the constant of proportionality of a differential polarization response to the optical spectrum of said signal contribution; estimating the optical spectrum of said noise contribution from said input optical signal, within said optical signal bandwidth using said constant of proportionality and said differential polarization response; and determining said in-band noise parameter on said input optical signal from the mathematically discriminated noise contribution.

In-band optical noise measurement using differential polarization response

In a method of measuring cumulative polarization mode dispersion (PMD) along the length of a fiber-under-test (FUT), a polarization-sensitive optical time domain reflectometer (POTDR) is used to inject into the FUT plural series of light pulses arranged in several groups. Each group comprises at least two series having closely-spaced wavelengths and the same state of polarization (SOP). At least two of such groups are injected and corresponding OTDR traces obtained for each series by averaging the impulse-response signals of the several series in the group. The process is repeated for a number of groups. The PMD is obtained by normalizing the OTDR traces of all of the groups, then computing the difference between each normalized OTDR trace in one group and the corresponding normalized OTDR trace in another group, followed by the mean-square value of the differences. Finally, the PMD is computed as a predetermined function of the mean-square difference.

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Normand Cyr