IEC 62803:2016

IEC 62803 ®
Edition 1.0 2016-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Transmitting equipment for radiocommunication – Frequency response of
optical-to-electric conversion device in high-frequency radio over fibre
systems – Measurement method
Matériels émetteurs pour les radiocommunications – Réponse en fréquence des
dispositifs de conversion optique-electrique dans des systèmes de transmission
radio sur fibre haute fréquence – Méthode de mesure

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IEC 62803 ®
Edition 1.0 2016-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Transmitting equipment for radiocommunication – Frequency response of

optical-to-electric conversion device in high-frequency radio over fibre

systems – Measurement method
Matériels émetteurs pour les radiocommunications – Réponse en fréquence des

dispositifs de conversion optique-electrique dans des systèmes de transmission

radio sur fibre haute fréquence – Méthode de mesure

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.060.20 ISBN 978-2-8322-3392-4

– 2 – IEC 62803:2016 © IEC 2016
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references. 7
3 Terms, definitions and abbreviations . 7
3.1 Terms and definitions . 7
3.2 Abbreviations . 9
4 Optical-to-electrical (O/E) conversion device . 9
4.1 Photo diode (PD) . 9
4.1.1 General . 9
4.1.2 Component parts . 9
4.1.3 Structure . 9
4.1.4 Requirements for PD . 10
4.2 DFG device . 10
4.2.1 General . 10
4.2.2 Component parts . 10
4.2.3 Structure . 10
4.2.4 Requirements for DFG device . 10
5 Sampling for quality control . 11
5.1 Sampling. 11
5.2 Sampling frequency . 11
6 Measurement method of frequency response . 11
6.1 Circuit diagram . 11
6.2 Measurement condition . 12
6.2.1 Temperature and environment . 12
6.2.2 Warming up of measurement equipment . 12
6.3 Principle of measurement method . 12
6.4 Measurement procedure . 13
Annex A (normative) Power balanced two-tone signal generation by using a high
extinction-ratio MZM [2] . 15
Annex B (informative) Requirements for the optical amplifier with automatic level
control . 17
B.1 Introductory remark . 17
B.2 Block diagram . 17
B.2.1 Optical amplifier . 17
B.2.2 Automatic level control . 18
B.3 Function and capabilities . 18
B.4 Requirements . 19
B.4.1 Optical amplifier . 19
B.4.2 Automatic level control (ALC) . 20
Annex C (informative) Frequency-response measurement system and automatic level
control EDFA . 21
C.1 Frequency response measurement system for optical-to-electric conversion
devices with a two-tone generator . 21
C.2 Automatic level control EDFA (ALC-EDFA) . 22
Bibliography . 24

Figure 1 – Definition of "conversion efficiency " . 8
Figure 2 – Optical-to-electrical conversion by photo diode . 10
Figure 3 – DFG device . 10
Figure 4 – Circuit diagram . 11
Figure B.1 – Block diagram of the optical amplifier . 17
Figure B.2 – Block diagram of the automatic level control . 18
Figure B.3 – Frequency characteristics . 19
Figure C.1 – System configuration for the frequency response measurement system . 21
Figure C.2 – ALC-EDFA system configuration. 22
Figure C.3 – Frequency response measurement examples . 23

Table C.1 – Typical specifications of the frequency response measurement system . 22
Table C.2 – Typical specifications of the ALC-EDFA system . 23

– 4 – IEC 62803:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TRANSMITTING EQUIPMENT FOR RADIOCOMMUNICATION –
FREQUENCY RESPONSE OF OPTICAL-TO-ELECTRIC CONVERSION
DEVICE IN HIGH-FREQUENCY RADIO OVER FIBRE SYSTEMS –
MEASUREMENT METHOD
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of 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, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). 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. 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 IEC on technical matters express, as nearly as possible, an international
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interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses
arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
International Standard IEC 62803 has been prepared by IEC technical committee 103:
Transmitting equipment for radiocommunication.
The text of this standard is based on the following documents:
FDIS Report on voting
103/147/FDIS 103/148/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.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this publication will remain unchanged until the
stability 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.
– 6 – IEC 62803:2016 © IEC 2016
INTRODUCTION
A variety of microwave-photonic devices are used in wireless communication and broadcasting
systems. A photo-receiver is an interface which converts an optical signal to an electronic signal.
This International Standard has been prepared to provide methods for evaluating and calibrating
high speed photo-receivers to be used in Radio over Fibre systems.
The method utilizes a Mach-Zehnder modulator for generating two-tone lightwaves as stimulus
signals, to provide simpler and easier methods than the conventional method utilizing a complex
two-laser system phase-locked with each other.
The International Electrotechnical Commission (IEC) draws attention to the fact that it is claimed
that compliance with this document may involve the use of a patent concerning a calibration
method and device for light intensity measuring instrument, as it relates to Clause 6.
Related part Patent holder Patent number
Clause 6 National Institute of Information and JP 4753137B
Communications Technology
EP1956353A
US7864330B
IEC takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured the IEC that he/she is willing to negotiate licences
either free of charge or under reasonable and non-discriminatory terms and conditions with
applicants throughout the world. In this respect, the statement of the holder of this patent right is
registered with IEC. Information may be obtained from:
National Institute of Information and Communications Technology
4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795, Japan

Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights other than those identified above. IEC shall not be held responsible for
identifying any or all such patent rights.
ISO (www.iso.org/patents) and IEC (http://patents.iec.ch) maintain on-line data bases of
patents relevant to their standards. Users are encouraged to consult the data bases for the most
up to date information concerning patents.

TRANSMITTING EQUIPMENT FOR RADIOCOMMUNICATION –
FREQUENCY RESPONSE OF OPTICAL-TO-ELECTRIC CONVERSION
DEVICE IN HIGH-FREQUENCY RADIO OVER FIBRE SYSTEMS –
MEASUREMENT METHOD
1 Scope
This International Standard provides a method for measuring the frequency response of
optical-to-electric conversion devices in wireless communication and broadcasting systems.
The frequency range covered by this standard goes up to 100 GHz (practically limited up to
110 GHz by precise RF power measurement) and the wavelength band concerned is 0,8 µm to
2,0 µm.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
There are no normative references in this document.
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
conversion efficiency
ratio of the output current to the input optical power defined by
ΔI
out
k = (1)
ΔP
in
Note 1 to entry: See Figure 1.

– 8 – IEC 62803:2016 © IEC 2016
ΔI
out
P (mW)
in
ΔP
in
IEC
Figure 1 – Definition of "conversion efficiency "
Note 2 to entry: Conversion efficiency k, which depends on modulating signal frequency,is often expressed in dB as
the ratio to the reference conversion efficiency of 1 (ampere per watt). It is well known, however, that dB has two
definitions. One is the optical conversion efficiency k [dB ] calculated from 10×log (∆I /∆P ), and the other is the
o o 10 out in
electrical conversion efficiency k [dB ] calculated from 20× log (∆I /∆P ). As for the conversion efficiency k, the
e e 10 out in
numerator is the amplitude of the electrical output signal, and the denominator is the power of optical input signal.
Therefore, both definitions of dB for conversion efficiency k and k are shown as follows:
o e
∆I
out
k = k [dB ] = 10 ∗log (2)
o o o 10
P
∆
in
∆I
out
k = k [dB ] = 20 ∗log (3)
e e e 10
∆P
in
3.1.2
two-tone lightwave
lightwave that contains two dominant spectral components whose power difference is relatively
small and frequency separation is stable
Note 1 to entry: Undesired spectral components are suppressed significantly. The measurement methods described
in this standard utilize a Mach-Zehnder modulator (MZM) for two-tone signal generation, where the MZM is biased at
maximum or minimum transmission points (null or full bias) [1] . The suppression ratio of undesired components
depends on the on-off extinction ratio and chirp parameter of the MZM. By using active trimming, high extinction-ratio
and low chirp modulation can be achieved for ideal two-tone generation (see Annex A).
3.1.3
carrier-suppressed
situation when an MZM is biased at its minimum transmission point, the non-modulated carrier
lightwave transmitted through and the two arms of the MZM are cancelled with each other at the
output coupler
Note 1 to entry: The suppression ratio is related to how the two lightwaves in the two arms have the same power and
to their anti-phase at the output coupler.
____________
Numbers in square brackets refer to the Bibliography.
I (mA)
out
3.2 Abbreviations
AGC-EDFA Automatic gain controlled-EDF amplifier
ALC Automatic level control
DFG Difference frequency generation
DUT Device under test
E/O Electrical-to-optical
EDFA Er-doped fibre amplifier
FPGA Field programmable gate array
LD Laser diode.
MZM Mach-Zehnder modulator
O/E Optical-to-electrical
OMI Optical modulation index
PD Photo diode
PN Positive-negative
RF Radio frequency
RoF Radio over fibre
VOA Variable optical attenuator

4 Optical-to-electrical (O/E) conversion device
4.1 Photo diode (PD)
4.1.1 General
A PD has a positive-negative (PN) junction which can be illuminated by an optical signal. When
a photon is incident to the PN junction, an electron is excited and an electron-hole pair is
generated. The electron and hole drift to the opposite direction because of the built-in and
reverse-biased voltage at the PN junction, and can be used as an output electric current.
4.1.2 Component parts
The O/E conversion devices consist of basic parts as follows:
– PD;
– input fibre pigtail (where appropriate);
– input receptacle (where appropriate);
– output RF port (where appropriate);
– bias electrode (where appropriate);
– transimpedance amplifier (where appropriate);
– impedance matching resistor (where appropriate).
4.1.3 Structure
The structure consists of the following (see Figure 2):
– optical input: fibre pigtail or receptacle;
– RF output: coaxial connector, microstrip line, coplanar waveguide, antenna, etc.;
– options: bias electrode, transimpedance amplifier, impedance-matching resistor.

– 10 – IEC 62803:2016 © IEC 2016
Optical RF
input output
PD
power current
IEC
Figure 2 – Optical-to-electrical conversion by photo diode
4.1.4 Requirements for PD
4.1.4.1 General
This method is based on a heterodyne principle. Requirements for the PD of this measurement
method are as follows.
4.1.4.2 Material of PD
Main materials of the PDs should be Si, GaAs, and InGaAs.
4.2 DFG device
4.2.1 General
When two coherent lightwaves are incident to a DFG device fabricated from a second order
nonlinear optical material, an RF signal with the difference frequency between the incident
lightwaves is generated.
4.2.2 Component parts
The component parts are as follows:
– DFG device;
– input optical lens (where appropriate);
– output RF antenna (where appropriate).
4.2.3 Structure
See Figure 3.
Optical RF
DFG
input output
device
beam wave
IEC
Figure 3 – DFG device
4.2.4 Requirements for DFG device
4.2.4.1 General
This method is based on the heterodyne principle. Requirements for the DFG device of this
measurement method are as follows.
4.2.4.2 Material
The main substrate materials of the DFG device should be materials such as LiNbO , LiTaO ,
3 3
KH PO , PZT (Pb (Zr, Ti) O3), PLZT ((Pb, La) (Zr, Ti) O3), InP, GaAs, InGaAs, InAlAs, InGaAsP,
2 4
Chromophore containing polymer, etc., which realize second order, nonlinear optical effect.

4.2.4.3 Device design
In general, the efficiency of the DFG is rather low. In order to enhance the conversion efficiency,
the device length tends to be long, and phase matching conditions must be satisfied. Moreover,
in order to avoid undesired RF wave radiation, an RF cavity or guiding structure is also required.
5 Sampling for quality control
5.1 Sampling
A statistically significant sampling plan shall be agreed upon by user and supplier. Sampled
devices shall be randomly selected and representative of production population, and shall
satisfy the quality assurance criteria using the proposed test methods.
5.2 Sampling frequency
Appropriate statistical methods shall be applied to determine adequate sample size and
acceptance criteria for the considered lot size. In the absence of more detailed statistical
analysis, the following sampling plan can be employed.
Sampling frequency for evaluation of frequency response: two units at least per manufacturing
lot.
6 Measurement method of frequency response
6.1 Circuit diagram
See Figure 4.
Point a
1 2 6 7 8 9 10
DC – 55 GHz
3 4 11
or
DC – 22,5 GHz
5 12
IEC
Key
1 Laser diode
7 Optical amplifier (optional)
2 MZM
8 Automatic level control (optional)
3 Bias tree
9 DUT
4 Microwave signal source (SC)
10 RF power meter or spectrum analyser
5 DC voltage source
11 Optical power meter (optional)
6 Optical band rejection filter (optional)
12 Personal computer
Figure 4 – Circuit diagram
– 12 – IEC 62803:2016 © IEC 2016
6.2 Measurement condition
6.2.1 Temperature and environment
The measurement should be carried out in a room at a temperature ranging from 5 °C to 35 °C.
If the operation temperature ranges of the measurement apparatuses are narrower than the
above range, the specifications of the measurement apparatuses should be followed. It is
desirable to control the measurement temperature within ±5 °C in order to suppress the
influence of temperature drift of measurement apparatuses to a minimum. The temperature of
the DUT can be changed using a temperature controller, as necessary.
6.2.2 Warming up of measurement equipment
The warming-up time shall be kept to typically 60 min, or the time written in the specifications of
the measurement equipment or systems.
6.3 Principle of measurement method
The method described here is based on the heterodyne principle. A two-tone lightwave
illuminates the DUT as a stimulus signal. The two-tone stimulus lightwave is generated by using
an MZM at null bias or an MZM at full bias with an optical band rejection filter. The average
powers of the input two-tone lightwave and that of the output monotone RF signal are measured,
and the conversion efficiency at the frequency is calculated from them. By changing the
frequency difference between the two tones, the frequency response of O/E conversion
efficiency of the DUT is obtained.
As is well known, an MZM optical output modulated by a monotone RF signal can be expressed
by
∞ ∞
i(ω t +φ )
n n
P = P
E = E e , ,P = [E ] , and ω = ω − ω (4)
opt n opt ∑ n
∑ n n RF n+1 n
n =∞ −∞
where P is the total average power, and ω is the angular frequency of the modulating RF
opt RF
signal that corresponds to the angular frequency difference between adjacent optical tones. As
an example, two-tone signal generation by an MZM with null-bias is described in 6.4. When
2 2 2
E = E >> E (n ≠ −1,+1) P ≅ E + E = 2E
, and (5)
−1 +1 n opt −1 +1 −1
an ideal well-balanced optical two-tone consisting of P (see 6.4) can be generated, where the
±1
following conditions should be satisfied:
a) suppression of optical carrier and higher order sidebands should be large enough;
b) frequency difference between the two desired components should be stable;
c) polarizations of the two spectral components should be well aligned;
d) power difference of the two spectral components should be small enough.
The instantaneous optical power P illuminating the PD is calculated as
opt
∞
i(ω t+φ ) i(ω t+φ ) i(ω t+φ )
−1 −1 +1 +1 n n
p = E e + E e + E e (n ≠ −1,+1)
opt −1 +1 n
∑
(6)
n=−∞
≅ P + P × cos(2ω t + φ)
opt opt RF
where φ = φ −φ , and E (n ≠ −1,+1) related terms are neglected from Equation (5). The PD
−1 +1 n
under test outputs a DC and an RF photocurrent as a response. The RF photocurrent i
RF
induced by the ideal well-balanced optical two-tone consisting of P or P is expressed as
±1 ±2
i = k ×P × cos(2ω t + φ) = I cos(2ω t + φ) (7)
RF e opt RF RF RF
where k is the conversion efficiency of the PD under test at 2ω , and i is the peak
e RF RF
photocurrent. ∆P is equal to P giving 100% OMI (optical modulation index) and ∆I is

in opt out
nearly equal to I k is described as
,
RF e
∆I I
out
RF
k = ≅ (8)
e
∆P P
in opt
where I is the amplitude of RF photocurrent induced by the ideal optical two tone.
RF
The average RF power P driving a load Z is expressed as
RF L
I Z
I I
L
RF RF RF
P = × Z = (9)
RF L
2 2
From Equations (7), (8) and (9), the squared k which corresponds to the responsivity of the PD
e
at the measurement frequency, is calculated as
I 2P
2 RF RF
k = = (10)
e
2 2
P Z P
opt L opt
Note that the squared k can be calculated only from the input optical and the output RF average
e
powers of the PD under test, if the ideal well-balanced optical two tone is launched, which are
traceable to the national standards with relatively short traceability chain. In this method, the
squared k does not depend on the frequency response of the MZM used for two-tone
e
generation.
6.4 Measurement procedure
Two types of measurement methods are described here. In Method A, a two-tone signal is
generated by an MZM with null bias, where the signal is composed of the first upper and lower
modulation side bands P . The frequency separation of the two-tone signal is equal to double
±1
the frequency of the signal fed to the MZM. In Method B, a two-tone signal is generated by an
MZM with full bias, where the modulator output is composed of the carrier P and the second
upper and lower modulation sideband P . By using an optical band rejection filter, the P
±2 0
component is eliminated to generate a two-tone signal consisting of P . The frequency
±2
separation of the two-tone signal is equal to quadruple the frequency of the signal fed to the
MZM. The optical amplifier and auto level control in Figures B.1 and B.2 can enhance the
frequency range of the measurement as described in Annexes B and C.
Method A
STEP 1) The measurement set-up is prepared as shown in Figures B.1 and B.2, where no
optical band rejection filter is needed.
STEP 2) The output signal of SG is set as follows.
Frequency: the half of the responsivity measurement frequency.

– 14 – IEC 62803:2016 © IEC 2016
Output power: when the unwanted third-order harmonic distortions should be
suppressed lower than –30 dB from the desired components, the signal power fed to
the MZM should be smaller than
0,085 ×V (f )
 
π
(11)
 
π
 
where, V (f) is the half-wavelength voltage at the modulating frequency.
π
STEP 3) The DC voltage applied to the MZM should be controlled to maintain the null bias.
STEP 4) The optical power meter measures the input average optical power P to the DUT
opt
at point “A”. When P is stabilized by ALC, it is not necessary to use the power
opt
meter.
STEP 5) The RF power meter measures the output average RF power P from the DUT.
RF
STEP 6) The conversion efficiency, k , at the measurement frequency is calculated by using
e
the following formula:
P
RF
k =
(12)
e
5P
opt
STEP 7) Repeat from STEP 2 to STEP 6 with a different frequency.
Method B
STEP 1) The measurement set-up is prepared as shown in Figures B.1 and B.2, where the
centre wavelength of the optical band rejection filter should be set to be the optical
output wavelength of the laser diode.
STEP 2) The output signal of SG is set as follows:
Frequency: 25 % of the conversion efficiency measurement frequency.
STEP 3) The DC voltage applied to the MZM should be controlled to maintain the full bias,
where the P component is eliminated by the optical band rejection filter.
STEP 4) The optical power meter measures the input average optical power P to the DUT
opt
at point “A”. When P is stabilized by ALC, it is not necessary to use the power
opt
meter.
STEP 5) The RF power meter measures the output average RF power PRF from the DUT.
STEP 6) The conversion efficiency, k, at the measurement frequency is calculated by using
Equation (12).
STEP 7) Repeat from STEP 2 to STEP 6 with a different frequency.

Annex A
(normative)
Power balanced two-tone signal generation by using
a high extinction-ratio MZM [2]

Annex A describes an example of two-tone signal generation using an MZM at null bias with high
extinction ratio. The bias point can be precisely controlled, when the extinction ratio is very high.
At the null bias condition, the power difference between the two desired spectral components
goes to the minimum.
Assuming a push-pull type MZM driven by a monotone RF signal of ω , its output lightwave can
RF
be expressed as
iω t
E e
 
input  η   η 
i{A sin(ω t +φ )+φ } i{A sin(ω t +φ )+φ }
1 RF 1 B1 2 RF 2 B2
E = L 1+ e + 1− e
   
 
2 2 2
   
 
(A.1)
i(ω t +φ )
∞
0 B1
E e
 η η 
input    
in(ω t +φ ) i(nφ +φ )
RF 1 B
= L e 1+ J (A + α )+ 1− J (− A + α )e
 n A n A 
∑
2 2 2
   
 
n=−∞
where L is the loss factor inside the MZM, and J (x) is the Bessel function of the first kind of order
n
n. The values of φ , φ , φ are the bias phases, η is the optical intensity imbalance, φ , φ , φ
B1 B2 B 1 2
are the skews, and A , A , A, α are the chirp related parameters defined as
1 2 A
2 2
 
L ×E
input
 η   η 
 
φ = φ − φ ,(P ,P ) = 1+  ,1−  ,η < 1
B B2 B1 1 2
 
(A.2)
4 2 2
   
 
φ = φ − φ ,(A ,A ) = (A + α ,− A + α ),A > α
2 1 1 2 A A A
Equations (A.1) and (A.2) are well known for showing good agreements with the actual
performance of MZMs, because four major error parameters of MZMs are all included [3, 4]. The
powers of the carrier, the upper sideband, and the lower sideband, (named “0”, “+1” and “-1”,
respectively) are derived as
L ×E
2 input
2 2
P = E = {R +S + 2RS cosφ }
0 0 B
L ×E
2 input
2 2
P = E = {T +U − 2TU cos(φ + φ)}
+1 +1 B
L ×E
input
2 2
{ ( )}
P = E = T +U − 2TU cos φ − φ (A.3)
−1 −1 B
η η
   
R = 1+ J (A + α ),S = 1− J (A − α )
0 A 0 A
2 2
   
 η   η 
T = 1+ J (A + α ),U = 1− J (A − α )
   
1 A 1 A
2 2
   
In the case of the MZM being biased at its minimum transmission point, which corresponds to the
case of φ =π, the powers of P , P , and P are calculated as
B 0 +1 –1
– 16 – IEC 62803:2016 © IEC 2016
L ×E
input
P = (R −S)
(A.4)
L ×E
input
2 2
P = P = {T +U + 2TU cosφ}
+1 −1
Equation (A.4) means that when the MZM is biased at a minimum transmission point, the carrier
power P becomes the minimum. Simultaneously, the upper and the lower sideband powers of
P and P become equal. Therefore, by adjusting the bias voltages of the high-ER MZM to
+1 -1
maintain the carrier power at minimum, the powers of the two tones automatically become equal.
Note that Equation (A.4) is satisfied independently from the other parameters of η, α , and φ.
A
Further, this technique is consistent with that of suppressing the carrier power. Monitoring the
carrier power is easier than measuring each power of the two-tone signal. In the frequency
response measurement, two different techniques are employed for the optical and RF method,
according to the measurement frequency range. For a frequency range higher than 10 GHz, a
narrow-band optical band-pass filter directly extracts the carrier lightwave and its optical power
is monitored. For a frequency range lower than 10 GHz, an RF spectrum analyser monitors the
RF signal from the reference PD, which has a practically flat frequency response from DC to
10 GHz.
Annex B
(informative)
Requirements for the optical amplifier with automatic level control

B.1 Introductory remark
Annex B describes the optical amplifier and the automatic level control system function and the
general requirements needed to realize these functions.
B.2 Block diagram
B.2.1 Optical amplifier
See Figure B.1.
10 11
1 4 6 5 1
2 7 2
3 8 3
IEC
Key
1 Optical coupler 7 Pump-LD
2 Photodiode 8 Driver for the pump-LD
3 Trans-impedance amplifier 9 FPGA (field programmable gate array)
4 Optical delay line 10 Optical input
5 EDF (er-doped fibre) 11 Optical output
6 Wavelength multiplexer
Figure B.1 – Block diagram of the optical amplifier

– 18 – IEC 62803:2016 © IEC 2016
B.2.2 Automatic level control
See Figure B.2.
7 8
6 3
IEC
Key
1 Optical coupler 5 Driver for the VOA
2 Photodiode 6 FPGA (field programmable gate array)
3 Trans-impedance amplifier 7 Optical input
4 VOA (variable optical attenuator) 8 Optical output
Figure B.2 – Block diagram of the automatic level control
B.3 Function and capabilities
The combination of an optical amplifier and an automatic level control (ALC) system can offer
enlarged frequency bandwidth as described in Figure B.3.
The output swept signals from an MZM are amplified by an AGC-EDFA (automatic gain
controlled-EDF amplifier). The VOA’s loss incorporated in the ALC system is set to an
appropriate value in advance. The frequency bandwidth can be enlarged by adjusting the loss of
the VOA. Therefore, a two-tone system with an optical amplifier and an ALC system allows wider
frequency bandwidth compared to an MZM.
If the power roll-off of the MZM approaches 6 dB per octave and the pre-set loss of the VOA is
set to 6 dB, the frequency bandwidth of the two-tone system can be doubled. If the power roll-off
of the MZM approaches 6 dB per octave and the pre-set loss of the VOA is set to 6 dB, the
frequency bandwidth of the two-tone system can be doubled.

(1) (2)
(3)
LD Modulator AGC-EDFA ALC
(2) Output of AGC-EDFA
(3) Output of ALC
(1) Output of modulator
Frequency (Hz)
IEC
Figure B.3 – Frequency characteristics
B.4 Requirements
B.4.1 Optical amplifier
Typical requirements for the combination system of AGC-EDFA and ALC as a measurement
system are a high-speed frequency-sweep with less than 1 ms and a low error measurement
with less than 0,2 dB.
The following list describes the AGC-EDFA requirements:
– function: AGC (automatic gain control);
– wavelength range: 1 530 nm to 1 562 nm;
– input power range:−24 dBm to −4 dBm;
– gain: 18 dB to 23 dB;
– gain error: 0,1 dB max.;
– noise figure: 6 dB max.
The transfer function of the AGC-EDFA feedback (FB) control system is given by:
G (s)×G (s)×G (s)×G (s)
1 2 3 4 (B.1)
T =
AGC−EDFA
1+G (s)×G (s)×G (s)×G (s)×G (s)
1 2 3 4 5
where
G (s) is the transfer function of the input-side PD and TIA;
G (s) is the transfer function of the driver for the pump-LD;
G (s) is the transfer function of the pump-LD;
G (s) is the transfer function of the EDF;
G (s) is the transfer function of the output-side PD and TIA.
Amplitude (dB)
– 20 – IEC 62803:2016 © IEC 2016
High-speed is not required for the FB control because an EDF has a sub-ms physical
response-speed. However, the loop gain should be of an appropriate large value to offer a small
gain error.
B.4.2 Automatic level control (ALC)
To realize a high-speed sweep-time, the VOA incorporated in the ALC system has to be a
high-speed type VOA, such as E/O (electro-optic)-type or A/O (acousto-optic)-type.
The main requirements are described hereunder:
– response speed: < 100 µs;
– insertion loss: < 0,3 dB;
– gain error: 0,1 dB max.
Here is a transfer function of the ALC FB-control system:
G (s)×G (s)×G (s)
1 2 3
(B.2)
T =
AGC−EDFA
1+G (s)×G (s)×G (s)×G (s)
1 2 3 4
where
G (s) is the transfer function of the driver for the VOA;
G (s) is the transfer function of the VOA;
G (s) is the transfer function of the EDF;
G (s) is the transfer function of the output-side PD and TIA.
An optimum design for frequency characteristics of the transfer function is needed in order to
have a high-speed response without instability and the loop gain should be of an appropriate
large value to offer a small gain error.

Annex C
(informative)
Frequency-response measurement system
and automatic level control EDFA

C.1 Frequency response measurement system for optical-to-electric
conversion devices with a two-tone generator
Figure C.1 shows the system configuration for the frequency response measurement system.
The system consists of a two-tone generator, an EDFA, an RF signal generator, an optical power
meter and an RF power meter. The frequency sweep measurement is executed by the RF signal
generator sweeping. The efficiency of O/E conversion devices can be calculated by optical and
RF power levels for each frequency.
The two-tone generator consists of a laser diode (LD), an external modulator, a monitor, a drive
circuit for the e
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