SIST EN 61281-1:2001

SLOVENSKI STANDARD
SIST EN 61281-1:2001
01-februar-2001
Fibre optic communication subsystems - Part 1: Generic specification (IEC 61281-
1:1999)
Fibre optic communication subsystems -- Part 1: Generic specification
Lichtwellenleiter-Kommunikationsuntersysteme -- Teil 1: Fachgrundspezifikation
Sous-systèmes de télécommunications par fibres optiques -- Partie 1: Spécification
générique
Ta slovenski standard je istoveten z: EN 61281-1:1999
ICS:
33.180.01 6LVWHPL]RSWLþQLPLYODNQLQD Fibre optic systems in
VSORãQR general
SIST EN 61281-1:2001 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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NORME
CEI
INTERNATIONALE
IEC
61281-1
INTERNATIONAL
STANDARD
Première édition
First edition
1999-01
Sous-systèmes de télécommunications
par fibres optiques –
Partie 1:
Spécification générique
Fibre optic communication subsystems –
Part 1:
Generic specification
 IEC 1999 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
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procédé, électronique ou mécanique, y compris la photo- including photocopying and microfilm, without permission in
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International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue

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61281-1  IEC:1999 – 3 –
CONTENTS
Page
FOREWORD . 5
Clause
1 Scope . 7
2 Normative references . 7
3 Definitions. 9
4 Symbols and acronyms . 31
4.1 Symbols. 31
4.2 Acronyms. 31
5 Subsystem characteristics . 35
5.1 General aspects. 35
5.2 Digital fibre optic subsystems . 41
5.2.1 General description . 41
5.2.2 Digital subsystem characteristics. 41
5.2.3 Digital transmitter characteristics. 43
5.2.4 Digital receiver characteristics . 45
5.2.5 Digital regenerator characteristics . 47
5.3 Analogue fibre optic subsystems . 49
5.3.1 General description . 49
5.3.2 Analogue subsystem characteristics . 49
5.3.3 Analogue transmitter characteristics . 51
5.3.4 Analogue receiver characteristics . 53
5.3.5 Analogue repeater characteristics. 55
5.4 Fibre optic links. 55
5.4.1 General description . 55
5.4.2 Fibre optic cable plant characteristics . 57
5.4.3 Fibre optic cable section characteristics. 57
5.4.4 Fibre optic splice and connector characteristics . 57
5.4.5 Optical device characteristics . 59
5.4.6 Optical fibre amplifier characteristics . 59
Annexes
A (informative) Document classification scheme for IEC 61280, IEC 61282
and IEC 61290 . 63
B (informative) Bibliography. 67

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61281-1  IEC:1999 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
FIBRE OPTIC COMMUNICATION SUBSYSTEMS –
Part 1: Generic specification
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61281-1 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
The text of this standard is based on the following documents:
FDIS Report on voting
86C/225/FDIS 86C/233/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
Annexes A and B are for information only.

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61281-1  IEC:1999 – 7 –
FIBRE OPTIC COMMUNICATION SUBSYSTEMS –
Part 1: Generic specification
1 Scope
This part of IEC 61281 is a generic specification for fibre optic communication subsystems
(FOCSs), and is structured according to the IEC Quality Assessment System (IECQ).
Subsystems are classified in families having a common sectional specification. Each sectional
specification is supplemented by blank detail specifications, and detail specifications
appropriate to the specific individual type or types of subsystems.
The parameters defined herein form a specifiable minimum set of specifications that are
common to all fibre optic subsystems. Additional parameters may be needed depending on
the particular application and technology. Those additional parameters will be specified in the
relevant sectional specification and/or detail specification, as appropriate.
Each specified parameter may be measured using one of the test procedures. The use of these
parameters for system design is given in design guides.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 61281. At the time of publication, the editions indicated
were valid. All normative documents are subject to revision, and parties to agreements based
on this part of IEC 61281 are encouraged to investigate the possibility of applying the most
recent editions of the normative documents indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
IEC 60793-2:1992, Optical fibres – Part 2: Product specification
IEC 60794-2:1989, Optical fibre cables – Part 2: Product specification
IEC 60874-1:1993, Connectors for optical fibres and cables – Part 1: Generic specification
IEC 61291-1:1998, Optical fibre amplifiers – Part 1: Generic specification

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61281-1  IEC:1999 – 9 –
3 Definitions
For the purpose of this part of IEC 61281, the following functional and operational definitions
apply. Within a definition, terms defined elsewhere are in italics.
3.1
active optical device
an optical device having gain of power
NOTE – Examples include active branching devices, optical amplifiers, optical modulators, optical regenerators,
and optical repeaters.
3.2
attenuation
the reduction of power (expressed in dB) between the end points of a fibre optic cable plant or
of a passive optical device
3.3
attenuator, optical
a passive optical device which produces a controlled signal attenuation when inserted in the
optical path
3.4
bandwidth
the difference (expressed in Hz) between the highest and lowest modulation frequencies at
which the modulus of the power spectrum or of the complex transfer function is one-half of the
peak value of the modulus
3.5
basic fibre optic system (BFOS)
the serial combination of a transmit terminal device, a fibre optic link, and a receive terminal
device
3.6
bit-error ratio (BER)
the number of errored bits divided by the total number of bits, over some stipulated period of
time
3.7
branching device (BD)
an optical device which has three or more optical ports
NOTE – Branching devices may be either passive (PBD) or active (ABD).
3.8
carrier-to-noise ratio (CNR)
the ratio (expressed in dB) of carrier power to noise power in a channel of defined bandwidth,
prior to any non-linear processing

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61281-1  IEC:1999 – 11 –
3.9
centre wavelength
the mean of the closest spaced half-power wavelengths, one above and one below the peak
wavelength of an optical spectrum
NOTE – Other spectral wavelengths are centroidal wavelengths, half-power wavelengths, and peak wavelengths.
3.10
centroidal wavelength
the mean or average wavelength of an optical spectrum
NOTE – Other spectral wavelengths are centre wavelengths, half-power wavelengths, and peak wavelengths.
3.11
chirping
a change of the wavelength or optical frequency of an intensity-modulated transmitter as a
function of the instantaneous intensity of the modulating signal
NOTE – When chirped signals are transmitted through optical fibre, the signal waveform is distorted by chromatic
dispersion. This process may cause a degradation in the quality of performance, designated as a chirping penalty.
3.12
combiner, optical
a wavelength-independent branching device in which the number of input ports exceeds the
number of output ports
3.13
connector, fibre optic
a fibre optic component providing optical interconnection/disconnection of fibre optic cable
sections, optical devices, and terminal devices
3.14
(chromatic) dispersion
the rate of change in group delay to wavelength (usually expressed in ps/nm) between the end
points of the fibre optic cable plant
3.15
environmental conditions
the range of temperatures, humidity, vibration levels, etc. within which the optical device can be
stored, or operated, or shipped and still meet all its specified parameter values
3.16
extinction ratio
in a digital transmission system, the ratio (expressed in dB) of the average power level of
logical "1" to the average power level of logical "0"
3.17
fibre optic cable plant (FOCP)
the serial combination of fibre optic cable sections, connectors, and splices providing the
optical path between two terminal devices, between two optical devices, or between a terminal
device and an optical device

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61281-1  IEC:1999 – 13 –
3.18
fibre optic cable section
a single (unjointed) optical fibre cable
3.19
fibre optic communication system
an assembly of fibre optic subsystems for transmitting information
3.20
fibre optic link (FOL)
the serial combination of a fibre optic cable plant and optical devices, providing the optical path
between a transmit terminal device and a receive terminal device
NOTE – This is equivalent to a basic fibre optic subsystem minus the transmitter and receiver.
3.21
fibre optic subsystem
an assembly of interconnected basic fibre optic subsystems. The assembly is specified at
defined interfaces within the fibre optic system
3.22
full-width at half-maximum (FWHM)
the positive difference of the closest spaced half-power wavelengths, one above and one below
the peak wavelength of an optical spectrum
NOTE 1 – Other spectral widths are N-dB-down widths and root-mean-square widths.
NOTE 2 – The FWHM equals the N-dB-down width where N = 3.
3.23
half-power wavelength
a wavelength corresponding to a half peak power value of the optical spectrum
NOTE – Other spectral wavelengths are central wavelengths, centroidal wavelengths, and peak wavelengths.
3.24
harmonic distortion
distortion in a system or transducer characterized by the presence at the output of spectral
*
components which are harmonically related to the spectral components of the input signal [1]
3.25
input power range
for an optical fibre amplifier, the range of optical power levels such that, for any input signal
power of the OFA which lies within this range, the corresponding output signal power lies in the
specified output power range, where the OFA performance is ensured
3.26
input signal bandwidth, analogue
the bandwidth at the electrical input to the transmitter
________
* Figures in square brackets refer to the bibliography given in annex B.

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61281-1  IEC:1999 – 15 –
3.27
intermodulation distortion (IMD)
distortion characterized by the appearance of spectral components with frequencies equal to
the sums and differences of integral multiples of two or more component frequencies of the
input signal [1]
3.28
intersymbol interference (ISI)
the overlap of adjacent pulses as caused by the limited bandwidth characteristics of the optical
devices in a fibre optic link
3.29
jitter
random or data-induced short-term non-cumulative variations of the phases or of the significant
instants of a digital signal from their ideal positions in time relative to a reference (clock) signal
NOTE 1 – In practice, "short-term" embraces all spectral components of 10 Hz and above.
NOTE 2 – Jitter is expressed in terms of absolute time or as a fraction of a unit interval.
3.30
jitter transfer function
the ratio of the output jitter to the applied input jitter as a function of modulation frequency
3.31
line bandwidth, optical
the interface signal bandwidth at the boundary between the fibre optic cable plant and the
terminal device
NOTE – See also transport bandwidth.
3.32
line bit rate, optical
the interface rate at the boundary between the fibre optic cable plant and the terminal device
NOTE – See also transport bit rate.
3.33
line code
a sequence of symbols that the binary data is converted into for purposes of transmission
NOTE 1 – Examples include Manchester, return-to-zero, block codes, digital scrambling, etc.
NOTE 2 – Line codes are used to recover timing, and in some cases they may be used to detect line errors, and to
convey additional information.
3.34
loss budget
the sum (expressed in dB) of the fibre optic link loss and the power penalty
power budget working margin
NOTE 1 – The loss budget equals the minus the .
NOTE 2 – The initial/final loss budget is the loss budget at the beginning/end of the life of the link.
NOTE 3 – The final loss budget equals the sum of the initial loss budget and the reserve margin.

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61281-1  IEC:1999 – 17 –
3.35
maximum receiver input power
a synonym for receiver overload
3.36
maximum reflectance tolerable at input
for an optical fibre amplifier, the maximum fraction of power, expressed in dB, exiting the input
port of the OFA, reflected into the OFA itself, for which the device still meets its specifications
NOTE – The measurement is performed with a given input signal optical power.
3.37
maximum reflectance tolerable at output
for an optical fibre amplifier, the maximum fraction of power, expressed in dB, exiting the
output port of the OFA, reflected into the OFA itself, for which the device still meets its
specifications
NOTE – The measurement is performed with a given input signal optical power.
3.38
maximum total output power
for an optical fibre amplifier, the highest optical power level at the output port of the OFA
operating within the absolute maximum ratings
3.39
modal bandwidth
the multimode fibre bandwidth due to differential mode attenuation and delay
NOTE 1 – It does not include chromatic dispersion.
NOTE 2 – It is measured using a source of narrow spectral width.
3.40
modal noise
noise generated in a fibre optic communication system by the combination of differential modal
attenuation and of fluctuations in the distribution of optical energy among the bound modes or
in the relative phases of the bound modes
3.41
mode partition noise (MPN)
noise due to the rapid fluctuation of the power distribution among the longitudinal modes of a
laser
NOTE – Due to the chromatic dispersion of the fibre optic cable plant, mode partition noise can produce signal
fluctuations at the receiver.
3.42
modulation factor/index
the ratio (expressed in %) of the peak optical signal of a transmitter modulated by an input
analogue signal to the average optical signal without any input signal
3.43
multipoint link
two or more fibre optic links that interconnect three or more terminal devices

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61281-1  IEC:1999 – 19 –
3.44
N-dB-down width
the positive difference of the closest spaced wavelengths, one above and one below the peak
wavelength, at which the spectral power density is N dB down from its peak value
NOTE – Other spectral widths are full-widths at half-maximum and root-mean-square widths.
3.45
noise figure
for an optical fibre amplifier, the decrease of the signal-to-noise ratio (SNR), at the output of
the optical detector, due to the propagation of a quantum-limited signal through the OFA,
expressed in dB
NOTE 1 – The operating conditions at which the noise figure is specified should be stated.
NOTE 2 – This property can be described at a discrete wavelength or as a function of wavelength.
NOTE 3 – The noise degradation due to the OFA is attributable to different contributions, for example: signal-
spontaneous beat noise, spontaneous-spontaneous beat noise, internal reflections noise, signal shot noise,
spontaneous shot noise. Each of these contributions depends on various conditions which should be specified for a
correct evaluation of the noise figure.
3.46
operating wavelength range
under consideration
3.47
optical amplifier
an active optical device that receives an optical input and retransmits it as an optical output of
increased power
NOTE – An example is an optical fibre amplifier (OFA).
3.48
optical connections
the splice type, connector type, and/or fibre type used as input and output ports of an optical
device
3.49
optical device
an optical component or assembly with one or more optical input ports and one or more optical
output ports
NOTE 1 – Optical devices can modify the information content of the optical input.
NOTE 2 – There are active optical devices and passive optical devices.
3.50
optical modulator
an optical device that modifies the intensity, frequency, phase, or polarization of an optical
carrier in accordance with an input signal
3.51
optical power
the amount of radiant energy per unit time that crosses a given section in the transmission
path. It is expressed in watts or, on the logarithmic scale, in dBm (where 0 dBm = 1 mW).

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61281-1  IEC:1999 – 21 –
3.52
optical regenerator or regenerative repeater (Rg)
an active optical device that receives, reshapes, retimes, and retransmits a digital optical
signal
3.53
optical repeater (Rp)
an active optical device that receives, improves, and retransmits an analogue optical signal
3.54
optical return loss (ORL)
the ratio (expressed in positive dB) of the incident power to the reflected power from an end
point of the fibre optic cable plant
NOTE – For reflected power from an optical device or terminal device, reflectance is the preferred term.
3.55
optical switch
an optical device that selectively routes an optical signal from one or more input ports to one or
more output ports
3.56
output power range
for an optical fibre amplifier, the range of optical power levels within which the output signal
optical power of the OFA lies, when the corresponding input signal power lies within the input
power range, where the OFA performance is ensured
3.57
passband, optical or wavelength bandwidth
the wavelength interval for an optical device within which the value of a particular parameter
lies within N-dB of its optimum value
3.58
passive optical device
an optical device having no gain of power
NOTE – Examples include optical attenuators and passive branching devices.
3.59
peak wavelength
the wavelength corresponding to the maximum power value of the optical spectrum
NOTE – Other spectral wavelengths are central wavelengths, centroidal wavelengths, and half-power wavelengths.
3.60
pigtail, fibre optic
under consideration
3.61
point-to-point link
a fibre optic link that connects a transmitter to a receiver

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61281-1  IEC:1999 – 23 –
3.62
polarization-dependent gain (PDG)
for an optical fibre amplifier, the maximum variation of the small-signal gain due to any
variation of the state of polarization of the input signal, at nominal operating conditions
3.63
power budget
the difference (in dB) between the transmitted optical power (in dBm) and the receiver
sensitivity (in dBm)
NOTE 1 – The power budget equals the sum of the loss budget and the working margin.
NOTE 2 – The initial/final power budget is the power budget at the beginning/end of the life of the transmitter and
receiver.
3.64
powering and control
for an optical fibre amplifier, those electrical currents and/or voltages, as well as those
electrical signals, necessary for OFA operation within the stated maximum ratings. Necessary
tolerances on electrical optical powering and switching on and off procedures are to be
included
3.65
power penalty
the increase of received optical power (expressed in dB) required to compensate for optical
transmission impairments at a specified quality of performance
NOTE – Impairments include distortion of the optical signal, dispersion and modal bandwidth of the fibre optic
cable plant, modal noise, etc. These include degradation due to reflections and to the combined effects of
intersymbol interference mode-partition noise chirping
, , and .
3.66
pump leakage to input
for an optical fibre amplifier, the pump optical power which is emitted from the OFA input port
NOTE 1 – The measurement is performed with a given input signal optical power.
NOTE 2 – The maximum pump leakage to input occurs for no input signal.
3.67
pump leakage to output
for an optical fibre amplifier, the pump optical power which is emitted from the OFA output port
NOTE 1 – The measurement is performed with a given input signal optical power.
NOTE 2 – The maximum pump leakage to output occurs for no input signal.
3.68
quality of performance
the criteria used to indicate a measure of transmission performance
bit-error ratio
NOTE 1 – The most common criterion for digital fibre optic systems is the .
NOTE 2 – The most common criteria for analogue fibre optic systems are the signal-to-noise ratio and the linearity.

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61281-1  IEC:1999 – 25 –
3.69
receiver, optical (Rx)
a terminal device with a single optical input and a corresponding single electrical output
3.70
receiver bandwidth
the bandwidth of the optical-to-electrical transfer function of an optical receiver
3.71
receiver dynamic range
the difference (expressed in dB) of the receiver overload (in dBm) and the receiver sensitivity
(in dBm)
3.72
receiver overload
the maximum receiver optical input signal average power above which a specified quality of
performance cannot be maintained
3.73
receive terminal device
a terminal device that converts one or more optical input signals into one or more electrical
output signals
3.74
receiver sensitivity
the minimum receiver optical input signal average power below which a specified quality of
performance cannot be maintained
3.75
reflectance
the ratio (expressed in negative dB) of the incident power to the reflected power from an optical
device or a terminal device
NOTE – For reflected power from an end point of the fibre optic cable plant, optical return loss is the preferred
term.
3.76
regenerative repeater or optical regenerator (Rg)
an active optical device that receives, reshapes, retimes, and retransmits a digital optical
signal
3.77
relative intensity noise (RIN)
for an analogue optical transmitter or repeater, the ratio (expressed in dB/Hz) of the average
fluctuation (per unit electrical frequency) in light power to the average desired light power
NOTE – RIN is usually measured within a narrow electrical passband as a function of input current or output power.

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61281-1  IEC:1999 – 27 –
3.78
reliability
for an optical fibre amplifier,
a) the minimum period of continuous operation without any faults at specified operating and
environmental conditions
b) the probability of faults per year at specified operating and environmental conditions
3.79
reserve margin
the difference (expressed in dB) between the final loss budget and the initial loss budget
3.80
root-mean-square width
the calculated r.m.s. value of a spectral power density
NOTE – Other spectral widths are full-width at half-maximum and N-dB-down width.
3.81
signal-to-noise ratio (SNR)
the ratio (expressed in dB) of the mean signal power (noise free) to the mean noise power
NOTE – The signal-to-noise ratio is sometimes expressed in equivalent terms of peak power ratio, or r.m.s. or peak
voltage ratios. Then the dB symbol should be annotated with the appropriate suffix in order to avoid ambiguity.
3.82
significant instant
the instant at which a signal element commences in a discretely timed signal [2]
3.83
small-signal gain (SSG)
for an optical fibre amplifier, the gain of the OFA, when operated in the linear regime, where it
is quite independent of the input signal optical power, at a given signal wavelength and pump
optical power level
NOTE – This property can be described at a discrete wavelength or as a function of wavelength.
3.84
spectral width
a measure of the wavelength extent of an optical spectrum
NOTE – Common measures include full-width at half-maximum, N-dB-down width, and root-mean-square width.
3.85
splice, fibre optic
a permanent or semi-permanent joint to couple optical power between two fibre optic cable
sections
3.86
splitter, optical
a wavelength-independent branching device in which the number of output ports exceeds the
number of input ports

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61281-1  IEC:1999 – 29 –
3.87
terminal device, fibre optic
a device that converts one or more electrical signals into one or more optical signals, or vice-
versa, and that is connected to at least one optical fibre
NOTE 1 – A fibre optic terminal device always has one or more integral connectors or pigtails.
NOTE 2 – Examples include a receive terminal device, a transmit terminal device, a transmitter, and a receiver.
3.88
timing bandwidth
the electrical bandwidth of the digital regenerator timing extractor (retiming) circuit
NOTE 1 – The circuit typically contains a high-Q element tuned to the signal
...