IEC 61280-2-5:1998 pdf download – Fibre optic communication subsystembasic test procedures- Part 2-5: Test procedures for digital systems -Jitter transfer function measurement

IEC 61280-2-5:1998 pdf download – Fibre optic communication subsystembasic test procedures- Part 2-5: Test procedures for digital systems -Jitter transfer function measurement.
1.1 Intent
The object of this test procedure is to measure the jitter transfer characteristic of an individual digital equipment as the ratio of the output jitter to the applied input jitter as a function of frequency.
1.2 SpecIfIcation
Jitter transfer requirements are specified in terms of jitter templates, which cover a specified gain.lrequency region. Such requirements are intended to ensure that clock recovery circuits and desynchronizer phase smoothing circuits adequately attenuate jitter. If the relationship between the jitter appearing at the input and output ports of a digital equipment can be described In terms of a linear process (both additive and homogeneous), then a narrowband measurement will characterize its jitter transfer performance and the term jitter transfer function is used.
2 NormatIve reference
The following normative document contains provisions which, through reference in this text, constitutes provisions of this part of IEC 61280. At the time of publication, the edition indicated was valid. All normative documents are subject to revision, and parties to agreements based on this part of IEC 61280 are encouraged to investigate the possibility of applying the most recent edition of the normative document Indicated below. Members of IEC and ISO maintain registers of currently valid International Standards
IEC 608251 :1993, Safety of laser products — Part 1: Equipment classification, requirements, and user’s guide
3 Apparatus
3.1 The following apparatus are required: jitter generator. digital signal generator, spectrum analyzer. and jitter receiver. The frequency synthesizer is optional.
3.2 In addition, the enhanced technique requires the following: sine-wave generator. frequency synthesizer with phase modulation, buffer amplifier, variable delay line, dividers, mixer, low-pass filter, phase meter, and voltmeter.
3.3 The demultiplexer technique also requires a multiplexer.
3.4 Safety
All tests, performed on optical fibre communication systems, or that use a laser or light- emitting diodes in a test set, shall be carried out with safety precautions in accordance with
IEC 60825-I
4 Test sample
The sample is the equipment under test.
5 Procedure
5.1 Basic technique
5.1.1 Perform a jitter tolerance measurement of the EUT (equipment under test) over the desired frequency range. ii
5.1.2 Connect the equipment as shown in figure 1, bypassing the EUT. Verify proper continuity, linearity, and error-free operation.
5.1.3 Set the frequency range on the spectrum analyzer as desired. Adjust the tracking oscillator output level on the spectrum analyzer to produce a tolerable jitter amplitude over the selected frequency range, which should be large enough to ensure adequate measurement accuracy, yet sufficiently small enough to preserve linear operation.
5.1.4 Setting the spectrum analyzer bandwidth as narrow as feasible, sweep the desired frequency range and record the 0 dB amplitude reference trace of the fesi equipment. (Setting a narrow spectrum analyzer bandwidth may allow a reduction In applied jitter amplitude with no loss in measurement accuracy.)
5.1.5 Reconnect the EUT as shown in figure 1. Verify proper continuity, linearity, and error-free operation.
5.1.6 Use the spectrum analyzer to sweep the selected frequency range and record the magnitude of the overall (test equipmenl and EUT) jitter transfer function.
5.1.7 To obtain the EUT jiller transfer function, subtract the 0 dB amplitude reference trace in 5.14 from the overall jitter transfer function recorded in 5.1.6.
5.1.8 Repeal 5.1.1 to 5.1.7 for a sufficient number of frequency ranges to characterize the overall frequency range of interest.
5.2 Enhanced technique
5.2.1 Perform a jitter tolerance measurement of the EUT over the desired frequency range.
5.2.2 Connect the equipment as shown in figure 2, bypassing the EUT. Verity proper continuity and error-free operahon.
5.2.3 Adjust the variable delay until the voltmeter indicates that the mixer output is at the centre of its linear region (for a passive mixer, this corresponds to 0 V d.c.).
5.2.4 Set the frequency of the sine-wave generator as desired. Adjust the sine-wave generator amplitude to produce a tolerable jitter amplitude, which Is large enough to ensure adequate measurement accuracy at the selected frequency, yet sufficiently small enough to preserve linear operation.
5.2.5 Set the frequency range of the spectrum analyzer to include the selected jitter frequency, and display the desired surrounding frequency band. Setting the spectrum analyzer bandwidth as narrow as feasible, record the 0 dB amplitude transfer reference level of the test equipment Zero the phase meter, or equivalently, record the 0 phase transfer reterence reading.