PD IEC TS 61941:2000 pdf download

PD IEC TS 61941:2000 pdf download.Optical fibres -Polarization mode dispersion measurement techniques for single-mode optical fibres.
3.2.3 Method C
3.2.3.1 Polarizer
The polarizer shall polarize over the full wavelength range of the source The polarizer
extinction ratio over the source spectral range should be ‘20 dB.
3.2.3.2 Beam splitter
The beam splitter of the interferomeler is used to split the Incident polarized light into two components propagating in the Interferometer’s arms. The splitter can be an optical fibre coupler or a cube beam splitter.
3.2.3.3 Interferometer
The interferonieter can be an air path type or a fibre type It can be of Michelson or MachZehnder type, and it can be located at the source or at the detector end of the device under test. A quarter wave plate. for example, can be used to remove the autocorrelation peak response of the interferometer,
3.3 Input optics (all methods)
An optical lens system or single.mode fibre pigtail may be employed to excite the test fibre. The power coupled into the fibre shall be stable for the duration of the test.
3.3.1 FIbr, pigtail
If pigtails are used, interference effects due to reflections should be avoided. This may require index matching materials or angled cleaves The pigtails shall be single-mode.
3.3.2 Optical lens system
If an optical lens system is used, some suitable means, such as a vacuum chuck, shall be used to stably support the input end of the fibre.
3.3.3 Cladding mode stripper
Any cladding mode power should be removed from the test fibre. Under most circumstances, the fibre coating will perform this function; otherwise, employ a device that extracts cladding mode power.
3.4 Output optics
The power emitted from the test fibre must be coupled onto the active region of the detection system (see fIgures 1 to 3). An optical lens system, a butt splice to a single-mode fibre pigtail, or an index-matched fibre-to-fibre coupling made directly to the detection system are examples of means that may be used.
3.5 Signal detection
For signal detection, an optical detector is used which is linear and stable over the range of intensities and measurement times that are encountered in performing the measurement. A typical system might include synchronous detection by a chopperflock-in amplifier, an optical power meter, optical spectrum analyzer, or a polarimeter To use the entire spectral range of the source, the detection system must have a wavelength range which includes the wavelengths produced by the light source.
3.6 Computational equipment
A digital computer may be used for purposes of equipment control, data acquisition and!or numerical evaluation of the data.
3.7 Output signal polarization adjustments Method A — Polarizer and analyzer
The angular orientation of the polarizers is not critical, but should remain fixed throughout the measurement. With weak mode coupling, some adjustment of the polarizer orientation may be helpful in maximizing the amplitude of the oscillations in figure 4 Alternatively, this may be achieved by rotation of the fibre(s) at splices or connectors.
The analyzer is not needed when a polarimeter is used for signal detection.
Method B — Polarimeter
For the Jones matrix method, a polarimeter Is used to measure (as a function of wavelength) the three output states of polarization corresponding to insertion of each of the three polarizers. For the SOP method, a polarimeter is used to measure the Stokes parameters as a function of wavelength. For both methods, the wavelength range of the polarimeter shall include the wavelengths produced by the light source.
4 Test sample
The test sample shall be a known length of single-mode optical fibre (Category B) which may or may not be cabled The sample and piglails must be fixed in position at a nominally constant temperature throughout the measurement. Standard ambient conditions shall be employed unless otherwise specified. In the case of installed fibres and cables, prevailing deployment conditions may be used.
Mechanical and temperature stability of the lest device may be observed by the following procedures: For method A, the output power from (tie fibre at a fixed wavelength is measured with the output analyzer in place. In a time period corresponding to a typical complete measurement, the output power change should be small relative to the changes produced by a wavelength increment. For method B, the output state of polarization of the test fibre on a Poincaré sphere display is viewed. In a time period corresponding to an adjacent pair of Jones matrix measurements, the output polarization change should be small relative to the change produced by a wavelength increment.
When it is important to minimize additional mode coupling, uncabled fibre shall be supported in some manner (usually on a reel having a minimum wind radius of 150 mm) with essentially zero fibre tension (typically less than 15 g) Alternative fibre conditions (e.g. a fibre shipping spool) may be used if it has been demonstrated that comparable results are obtained.
End faces for the input and output ends of the test sample must be prepared as appropriate for the requirements of sections apparatus and procedure. The requirements of method IEC 60793-1-CiA of IEC 60793-1-4 should be observed as appropriate.