IEC TR 61282-8:2006

Fibre optic communication system design guides - Part 8: Calculating dispersion penalty from measured time-resolved chirp data

This part of IEC 61282 provides definitions of dispersion penalty and other related penalties. It describes the direct measurement of these penalties using a BER test set and the calculation of the penalties from time-resolved chirp (TRC) data. Annex A provides the theory for power penalty calculations.

General Information

• Status: Published
• Publication Date: 14-Nov-2006
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 33.180.01 - Fibre optic systems in general
• Technical Committee: SC 86C - Fibre optic systems and active devices
• Drafting Committee: WG 1 - TC 86/SC 86C/WG 1
• Current Stage: PPUB - Publication issued
• Start Date: 31-Oct-2006
• Completion Date: 15-Nov-2006

Standards Content (Sample)

TECHNICAL IEC
REPORT TR 61282-8
First edition
2006-11
Fibre optic communication system
design guides –
Part 8:
Calculating dispersion penalty from
measured time-resolved chirp data
Reference number
IEC/TR 61282-8:2006(E)
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TECHNICAL IEC
REPORT TR 61282-8
First edition
2006-11
Fibre optic communication system
design guides –
Part 8:
Calculating dispersion penalty from
measured time-resolved chirp data
© IEC 2006 ⎯ Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
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For price, see current catalogue

– 2 – TR 61282-8 © IEC:2006(E)
CONTENTS
FOREWORD.3
INTRODUCTION.5

1 Scope.6
2 Normative references .6
3 Terms and definitions .6
4 Measuring dispersion penalty using a bit-error-ratio test set .7
5 Obtaining time-resolved chirp data .8
6 Calculating dispersion penalty from time-resolved chirp data.9
6.1 Calculate BER for a particular condition .9
6.2 Calculate dispersion penalty.10
6.3 Calculate transmitter and dispersion penalty .11
6.4 Calculate total transmitter power penalty.11
7 An example measurement and calculation of power penalties.11
8 A comparison of dispersion penalty measurements from BER and TRC
measurements.12

Annex A (informative) Data analysis of bit error ratio versus received power in digital
systems .13

Bibliography.20

Figure 1 – Equipment setup for direct power penalty measurements .8
Figure 2 – Typical TRC data suitable for dispersion penalty calculations.9
Figure 3 – An example measurement of the three power penalties.12
Figure 4 – Comparison of dispersion penalty results for measurements with a BER test
set and for calculation from TRC data .12
Figure A.1 – Plot of Equation (A.1) with SNR plotted linearly .14
Figure A.3 – Example plot and analysis using the exact procedure. .18
Figure A.4 – Example plot and analysis using the log-log procedure .19

Table A.1 – Values for BER versus SNR .15
Table A.2 – Experimental data for exact linearization.18
Table A.3 – Experimental data for log-log analysis.19

TR 61282-8 © IEC:2006(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC COMMUNICATION SYSTEM DESIGN GUIDES –

Part 8: Calculating dispersion penalty
from measured time-resolved chirp data

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
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data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 61282-8, which is a technical report, has been prepared by subcommittee 86C: Fibre
optic systems and active devices, of IEC technical committee 86: Fibre optics.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
86C/686/DTR 86C/721/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.

– 4 – TR 61282-8 © IEC:2006(E)
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 61282 series, published under the general title Fibre optic
communication system design guides, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

TR 61282-8 © IEC:2006(E) – 5 –
INTRODUCTION
Dispersion penalty is a commonly used parameter of laser transmitters and is usually included
as a specification for transmitters designed for 2,5 Gb/s and higher data rates. The value of
the dispersion penalty is a function of the interaction of laser chirp, spectral width and fibre
dispersion and will depend on the particular type of fibre.
Because the type and length of the fibre specified for a particular transmitter is fixed, the
dispersion penalty is determined by the temporal characteristics of the transmitter chirp, which
include the spectral characteristics of the laser.
As developers and manufacturers of laser transmitters are attempting to go to higher rates
and longer distances, they are finding that chirp is limiting their ability to achieve a required
dispersion penalty. Direct measurement of dispersion penalty requires two BER
measurements over a reference receiver input range that yields BER values typically from
–4 –12
10 to 10 . This is typically a long measurement. Measuring time-resolved chirp (TRC) and
calculating dispersion penalty can be a considerably shorter measurement.
This technical report describes the procedure for calculating dispersion penalty from TRC
data.
– 6 – TR 61282-8 © IEC:2006(E)
FIBRE OPTIC COMMUNICATION SYSTEM DESIGN GUIDES –

Part 8: Calculating dispersion penalty
from measured time-resolved chirp data

1 Scope
This part of IEC 61282 provides definitions of dispersion penalty and other related penalties.
It describes the direct measurement of these penalties using a BER test set and the
calculation of the penalties from time-resolved chirp (TRC) data. Annex A provides the theory
for power penalty calculations.
The calculations are valid for all types of single longitudinal mode (SLM) laser transmitters
intended for use in telecommunications applications at data rates of 2,5 Gbit/s and higher with
NRZ modulation format. These include but are not limited to directly modulated DFB lasers,
DFB lasers with integrated electro-absorption modulators, and DFB lasers with external Mach-
Zehnder modulators. This technique is not suitable for multiple longitudinal mode (MLM)
lasers or LEDs.
Chromatic dispersion induced power penalty values in this technical report are characteristics
of the transmitter, which is considered to be the device-under-test (DUT). Other power penalty
sources, such as nonlinear effects and amplifier noise are not covered by this document.
Since dispersion penalty for a transmission link depends on the transmitter, receiver and
fibre, the dispersion penalty parameter for a transmitter is based on a specified fibre
dispersion and receiver characteristic, which should be reported with the test results.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 61280-2-8, Fibre optic communication subsystem test procedures – Digital systems –
Part 2-8: Determination of low BER using Q-factor measurements
IEC 61280-2-10, Fibre optic communication subsystem test procedures – Digital systems –
Part 2-10: Time-resolved chirp and alpha-factor measurement of laser transmitters
ITU-T Recommendation G.957, Optical interfaces for
...