IEC 60793-1-40:2001 pdf download
IEC 60793-1-40:2001 pdf download.ptical fibres -art 1-40: Measurement methods and test procedures -Attenuation.
9.2 Method C See annex C.
9.3 Method 0 See annex D.
10 Results
10.1 Information available with each measurement Report the following information with each measurement:
– date and title of measurement:
— identification of specimen;
— optical source wavelength:
— specimen length;
— spectral attenuation, dB, or attenuation coefficient, dBlkm, versus wavelength or at specific wavelength(s), as required by the detail specification,
10.2 Information available upon request
The following information shall be available upon request:
— measurement method used: A, B, C, or D;
— type of optical source used: central wavelength(s) and spectral width(s);
— launching technique and conditions used:
— Indication if a dead.zone fibre was used;
— descnption of all key equipment;
— for type B fibres — dimensions and number of turns of the mode filter or mode scrambler; pulse duration(s), scale range(s), and signal-averaging details;
— details of computation technique (calculation method):
— any deviations to the procedure that were made;
– date of latest calibration of measurement equipment,
For methods C and D. see the additional requirements in 0.5 of annex C and In 05 of annex D. respectively. This particularly applies when using method C fOr measuring point discontinuities.
11 SpecIfication InformatIon
The detail spec*flcation shall specify the following Information:
— type of fibre (or cable) to be measured;
– failure or acceptance criteria at the wavelength or wavelength range;
— any deviations to the procedure that apply;
— information to be reported.
The cut-back technique is the only method directly derived from the definition of fibre attenuation, in wtiich the power levels. P1(A) and P2(A). are measured at two points of the fibre without change of input conditions. P2(A) is the power emerging from the end of the fibre, and P1(a) is the power emerging from a point near the input after cutting the fibre. (This explain5 its wide acceptance as the reference test method for attenuation.)
This measurement principle does not permit information on the attenuation behaviour over the length of the fibre. Neither is it easy to measure the change of attenuation under changing conditions. In some situations, its destructive nature is a disadvantage.
A..1 Apparatus
*1.1 General apparatus for all fibres
See figures A.1 and A.2 for diagrams of suitable test set-ups.
A.1.1.1General launch arrangement
Figure A.3 shows the general launch arrangement used for all fibres. See A.1.2 to A.1.4 forfurther details as they apply to specific categories of single-mode and multimode fibres.
A.1.1.2Optical source
Use a suitable radiation source， such as a lamp,laser or light emitting diode.The choice ofsource depends upon the type of measurement.The source shall be stable in position, intensityand wavelength over a time period sufficiently long to complete the measurement procedure.Specify the spectral line width (between the 50 % optical intensity power points of the sourcesused) such that the line width is narrow,for example less than 10 nm,compared with anyfeatures of the fibre spectral attenuation.Align the fibre to the launch cone，or connect itcoaxially to a launch fibre.
A.1.1.3Source wavelength
Measurements may be made at one or more wavelengths. Alternatively, a spectral responsemay be required over a range of wavelengths.
A.1.1.4Optical detection assembly
Means shall be provided to couple all power emitted from the specimen to the active region ofthe detector. For example,an optical lens system, a butt spliced to a fibre pigtail, or couplingdirectly to the detector may be used. If the detector is already pigtailed,the pigtail fibre shallhave sufficiently large core diameter and numerical aperture to capture all of the light exitingthe reference and specimen fibres.
Use an optical detector that is linear and stable over the range of intensities and measurementtimes that are encountered in performing this measurement.A typical system might include aphotovoltaic mode photodiode amplified by a current input amplifier，with synchronousdetection by a lock-in amplifier.
A.1.1.5Signal processing
lt is customary to modulate the light source in order to improve the signal/noise ratio at thereceiver. If such a procedure is adopted，link the detector to a signal processing systemsynchronous with the source modulation frequency. The detecting system should be sub-stantially linear or have known characteristics.
