IEC 61280-2-5:1998 pdf download.Fibre optic communication subsystem basic test procedures – Part 2-5: Test procedures for digital systems – Jitter transfer function measurement
1 Scope and object
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/frequency 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 61 280. 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 61 280 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 60825-1 :1 993, Safety of laser products – Part 1 : Equipment classification, requirements,
and user’s guide
3 Apparatus
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 60825-1 .
4 Test sample
The sample is the equipment under test.
5 Procedure
5.1Basic technique
5.1.1 Perform a jitter tolerance measurement of the EUT (equipment under test) over the
desired frequency range. 1 )
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 test 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 equipment and EUT) jitter transfer function.
5.1.7 To obtain the EUT jitter transfer function, subtract the 0 dB amplitude reference trace
in 5.1 .4 from the overall jitter transfer function recorded in 5.1 .6.
5.2.2 Connect the equipment as shown in figure 2, bypassing the EUT. Verify proper
continuity and error-free operation.
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 reference
reading.
5.2.6 Reconnect the EUT as shown in figure 2. Verify proper continuity, linearity, and
error-free operation.
5.2.7 Use the spectrum analyzer to display the output jitter over the selected frequency range.
Record the overall (test equipment and EUT) output jitter amplitude and phase at the selected
jitter frequency.
IEC 61280-2-5:1998 pdf download
