IEC 61280-1-3 pdf download – Fibre optic communication subsystem test procedures – Part 1-3: General communication subsystems – Central wavelength and spectral width measurement

IEC 61280-1-3 pdf download – Fibre optic communication subsystem test procedures – Part 1-3: General communication subsystems – Central wavelength and spectral width measurement
4.2Power supplies
As required for the device under test.4.3Input signal source or modulator
The input signal source is a signal generator or modulator with the appropriate digital oranalogue signal of the system.
4.4Test cord
Unless otherwise specified, the physical and optical properties of the test cords shall match tothe cable plant with which the equipment is intended to operate.The cords shall be 2 m to5 m long,and shall contain fibres ‘with coatings which remove cladding light. Appropriateconnectors shall be used. Single-mode cords shall be deployed with two 90 mm diameterloops or otherwise assure rejection of cladding modes. if the equipment is intended formuitimode operation and the intended cable plant is unknown,the fibre size shall be50/125 um.
5Test sample
The test sample shall be a specified fibre optic subsystem，transmitter,or light source.Thesystem inputs and outputs shall be those normally seen by the user. The spectral widthparameters are typically used for characterizing MLM and LED transmitters. The width ofMTM and SLM lasers without modulation are normally too narrow to measure with thedispersive spectral instruments used with this method，Modulated SLM transmitters havebroadened linewidths for high data rates (above about 2,5 Gb/s) and due to chirp that may bemeasurable by this method.
WARNING – Exercise care to avoid possible eye damage from looking into the end of anenergized fibre from any light source.Most importantly， avoid looking into any energized fibreusing any type of magnification device.
The requirements in lEC 60825-1 shall be followed.
6Procedure (Method A)
6.1General
Method A is designed for the use of typical commercial optical spectrum analyzer instrumentsthat allow quick measurement of spectra with 1 000 wavelength samples or more,and allowsfor the analysis of such spectra based on all of the samples rather than selecting for exampleonly the samples at the peaks of mode wavelengths. The previous method using a smallernumber of discrete wavelength points is included in Clause 7 as Method B, for compatibilitywith the first edition of this standard. Method A has the advantage of easier”simplerautomated analysis and better representation of complex but narrow spectra,such asmultitransverse-mode vertical cavity surface emitting lasers (vCSELs). Due to its convenienceand prevalence in the industry,Method A is considered the reference test method.
6.2Setup
6.2.1 Use appropriate handling procedures to prevent damage from electrostatic discharge(ESD), which can cause opto-electronic devices to fail.
6.2.2 With the exception of ambient temperature，standard ambient conditions shall be used,unless otherwise specified.The ambient or reference point temperature shall be 23 C±2°C,unless otherwise specified.
6.2.3 Unless otherwise specified, apply a modulated input signal to the optical source. Allow sufficient time (per manufacturer’s recommendation or as specified in the detail specification) for the optical source/transmitter to reach a steady-state temperature.
6.2.4 Turn the optical spectrum analyzer on, and allow the recommended warm-up and settling time to achieve rated measurement performance level. 6.2.5 Connect the optical output of the optical source under test to the optical input connector of the optical spectrum analyzer. If the transmitter under test does not include isolation from back-reflections, as often the case at 850 nm, these reflections can cause the spectrum to be unstable and should be reduced with high return-loss connections and possibly external isolation or attenuation at the transmitter output.
6.3 Adjustment of spectrum analyzer controls
6.3.1 Using the resolution control, select an appropriate resolution (see 4.1 ). Typically less than 1 /1 0 of the spectral width to be measured, or the finest available resolution bandwidth (0,1 nm or narrower) should be used. Set the number of data points in the acquired signal to be sure to adequately sample the detail of the optical spectrum. Typically, this is set to at least 4 times the sample resolution times the total measured width. For example, a 1 0 nm measurement span, using 0,1 nm resolution, requires a minimum of 400 points in the measurement (4 × (total span)/resolution).
6.3.2 Using the span control, select an appropriate span of wavelength range on the display section of the spectrum analyzer. Initially select a sufficiently wide span to determine the appropriate position of the peak wavelength; then reduce and adjust the span again to fit all of the source spectrum or at least all that is within at least 20 dB of the peak power. For SLM lasers, the span may need to be changed, typically from 2 nm to 20 nm full scale, to determine the spectral width and SMSR.
6.3.3 Using the gain or reference level control, select a gain or reference level so that the amplitude of the peak output extends over the entire screen vertical scale.
6.3.4 If available, use the spectrum analyzer log-scale for amplitude measurement, to achieve the maximum dynamic range
6.3.5 For OSAs that are not capable of performing the subsequent calculations in Clause 8 internally, download the measured optical spectra data to a computer for further analysis in a format that contains both the wavelength and amplitude of all points in the measurement.