1、TECHNICAL REPORT IECTR 61292-2 First edition 2003-01 Optical amplifier technical reports Part 2: Theoretical background for noise figure evaluation using the electrical spectrum analyzer Reference number IEC/TR 61292-2:2003(E)Publication numbering As from 1 January 1997 all IEC publications are issu
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8、 919 03 00TECHNICAL REPORT IEC TR 61292-2 First edition 2003-01 Optical amplifier technical reports Part 2: Theoretical background for noise figure evaluation using the electrical spectrum analyzer PRICE CODE IEC 2003 Copyright - all rights reserved No part of this publication may be reproduced or u
9、tilized 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 Varemb, PO Box 131, CH-1211 Geneva 20, Switzerland Telephone: +41 22 919 02 11 Telefax: +41 22 9
10、19 03 00 E-mail: inmailiec.ch Web: www.iec.ch F For price, see current catalogue Commission Electrotechnique Internationale International Electrotechnical Commission 2 TR 61292-2 IEC:2003(E) CONTENTS FOREWORD 3 INTRODUCTION 4 1 Scope and object . 5 2 Normative references. 5 3 Theoretical background
11、of calibration . 5 3.1 Calculation for photocurrent measurement alternative . 7 3.2 Calculation of source RIN 7 4 Theoretical background of noise factor calculation 8 Annex A (informative) List of symbols and abbreviations .11 Figure 1 Noise figure calibration setup. 5 Figure 2 Equipment for electri
12、cal noise figure test 8TR 61292-2 IEC:2003(E) 3 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ OPTICAL AMPLIFIER TECHNICAL REPORTS Part 2: Theoretical background for noise figure evaluation using the electrical spectrum analyzer FOREWORD 1) The IEC (International Electrotechnical Commission) is a world
13、wide 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 othe
14、r 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
15、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
16、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, t
17、echnical specifications, 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
18、 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 conf
19、ormity with one of its standards. 6) Attention is drawn to the possibility that some of the elements of this technical report may be the subject of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights. The main task of IEC technical committees is to prep
20、are International Standards. However, a technical committee may propose the publication of a technical report when it has collected data of a different kind from that which is normally published as an International Standard, for example state of the art. IEC 61292-2, which is a technical report, has
21、 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/418/DTR 86C/474/RVC Full information on the voting for the approval of th
22、is technical report 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 2008. At this date, the publication
23、will be reconfirmed; withdrawn; replaced by a revised edition, or amended. 4 TR 61292-2 IEC:2003(E) INTRODUCTION This Technical Report should be read in conjunction with IEC 61290-3-2. To enhance the clarity of this document, some of the text in document 61290-3-2 is repeated here. Definitions of ma
24、ny terms and parameters contained in this Technical Report can be found in IEC 61291-1. Each abbreviation introduced in this Technical Report is generally explained in the text the first time it appears. However, for an easier understanding of the whole text, a list of the abbreviations used in this
25、 Technical Report is given in Annex A.TR 61292-2 IEC:2003(E) 5 OPTICAL AMPLIFIER TECHNICAL REPORTS Part 2: Theoretical background for noise figure evaluation using the electrical spectrum analyzer 1 Scope and object This Technical Report applies to all commercially available optical amplifiers (Oas)
26、 including optical fibre amplifiers (OFAs) using active fibres and semiconductor optical amplifiers (SOAs) using semiconductor gain media. The object of this Technical Report is to provide the theoretical background to Clause 6 (Calculation) of IEC 61290-3-2. 2 Normative references The following ref
27、erenced 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 61290-3: Optical fibre amplifiers Basic specification Test met
28、hods for noise figure parameters IEC 61290-3-2: Optical fibre amplifier test methods Part 3-2: Noise figure parameters Electrical spectrum analyzer method IEC 61291-1: Optical fibre amplifiers Part 1: Generic specification 3 Theoretical background of calibration The calibration setup is shown in Fig
29、ure 1. dB Source module Variable input attenuator DFB laser with isolator Modulation source Receiver module Detector ESA Variable output attenuator Electrical amplifier Optical power meter Power meter jumper cable Polarisation controller dB Possibly separable Optical filter (optional) El. spectrum a
30、nalyser IEC 2970/02 Figure 1 Noise figure calibration setup 6 TR 61292-2 IEC:2003(E) The following quantities are obtained during the calibration process; notice that all noise measurement results are to be understood as ESA power levels after subtraction of the thermal noise level: P in,0 is optica
31、l input power at 0 dB setting of input attenuator. S 0is electrical power of the modulation signal at 0 dB setting of input attenuator. N 0 is noise power measured with ESA with input and output attenuator at 0 dB. N 0 is noise power measured with ESA with input attenuator set to 1/k (k 1) and outpu
32、t attenuator set to 0 dB. N 0can be expressed as: 0 shot, 0 rin, 0N N N + = W (1) N rin,0 is (frequency-dependent) ESA noise contribution caused by the lasers relative intensity noise (RIN); N shot,0 is (frequency-independent) ESA noise contribution caused by the photodetectors shot noise. N 0 , obt
33、ained after k-fold reduction of the input power, can be expressed as: 0 shot, 0 , rin 2 0N k N k N + = (2) For subtraction purposes, re-write equation (2) in two different forms: 0 shot, 0 rin, 0 2 11 N k N N k + = (3) 0 shot, 0 rin, 01 N N k N k + = (4) Subtraction (3) (1) yields the shot noise con
34、tribution to the ESA noise power:0 0 2 0 shot,11 1 N N k k N = () k k N k N N10 2 0 0 shot, = (5) Subtraction (1) (4) also yields the contribution from the sources RIN to the ESA noise power:() 0 0 0 rin, 11 N k N k N = () k k N N k N10 0 0 rin, = (6)TR 61292-2 IEC:2003(E) 7 3.1 Calculation for phot
35、ocurrent measurement alternative The effective photodetector responsivity (which includes the loss of the output attenuator at 0 dB attenuation) can be calculated from: in,0 pd,0 0P I r = Calculate the shot- and RIN contributions using: e e x B P H r e B T R P r e N in,0 0 0 2 in,0 0 0 shot, 22 = =
36、(7) 2 in,0 2 0 0P m H S = 8) in which m is the ratio of RMS optical power modulation amplitude to average optical power, and the following was used as receiver transfer function: R T r P S H x 2 2 0 2 in esa 0= = (9) where r 0 is effective photodetector responsivity in A/W through output attenuator
37、at 0 dB setting; this quantity may depend on the baseband frequency, and T x is voltage amplification between resistor R and ESA input; this quantity usually depends on the baseband frequency. Dividing the two equations yields: in,0 2 0 2 in,0 2 0 in,0 0 0 0 0 shot,22P m B r e P m H B P H r e S N e
38、e = = (10) in,0 2 0 0 0 shot,2P m S B r e N e = (11) 3.2 Calculation of source RIN The following derivation can be used to estimate the laser RIN: source 2 in,0 0 0 rin,RIN P B H N e = (12) e e x B P H r e B T R P r e N in,0 0 0 2 in,0 0 0 shot, 22 = = (13) 8 TR 61292-2 IEC:2003(E) Dividing the two
39、equations yields: e RIN P r B P H r e RIN P B H N N e e 22source in,0 0 in,0 0 0 source 2 in,0 0 0 shot, 0 rin, = = (14) and = 0 shot, 0 rin, in,0 0 source2 lg 10 N N P r e RIN dB(Hz 1 ) (15) For the purpose of this procedure, it is sufficient to know the approximate RIN value. Therefore, it may be
40、sufficient to estimate the value of r 0in the equation above. 4 Theoretical background of noise factor calculation Purpose and strategy: subtract shot noise and RIN contributions from the measured electrical spectrum analyzer (ESA) noise powers, then add the theoretical shot noise contribution of an
41、 ideal photodetector with quantum efficiency = 1. Notice that the shot noise and spontaneous- spontaneous mixing contributions caused by the amplified source spontaneous emission are neglected. In the following, subscript 0 denotes source quantities and subscript 1 denotes quantities when the OA is
42、inserted. An asterisk * denotes quantities measured with an ideal photodetector with quantum efficiency = 1. dB Source module Variable input attenuator DFB laser with isolator Modulation source Receiver module Detector ESA Variable output attenuator Electrical amplifier OA under test Optical power m
43、eter Power meter jumper cable Polarisation controller dB Possibly separable Optical filter (optional) IEC 2971/02 Figure 2 Equipment for electrical noise figure test Most equations in this clause are in linear, not logarithmic form. The equations below make use of previous measurement and calibratio
44、n results. Results obtained from the calibration: P in,0 , N th , S 0 , N shot,0 , N rin,0 , B e. Results obtained from measurement: T in , T out,P out , S 1 , N 1.TR 61292-2 IEC:2003(E) 9 a) Calculate the (frequency-dependent) total noise factor as outlined in the noise figure theory of IEC 61290-3
45、: * * * * *1 1 OA, 1 shot, 0 shot, 0 out in S N N N S SNR SNR F + = = (16) b) The first ratio of the noise factor can be expressed in photocurrents from an ideal photodetector: e e B h P m B P e h P m h e N S 22* * in 2 in 2 2 in 2 2 0 shot, 0 = = (17) where h eis the responsivity of an ideal photod
46、etector, and 0 in, in inP T P = is the input power. c) The second ratio of the noise factor can be re-written by replacing the OA-term with ESA measurement results; it does not depend on the quantum efficiency of the photodetector: 1 1 OA, 1 1 shot, 1 1 OA, 1 shot,* * * * S N S N S N N + = + (18) 1)
47、 Analysis of the first term, expressed in photocurrents from an ideal photodetector: 2 in 2 2 out 2 in 2 2 2 out 2 1 1 shot, 2 1 2 * * P G m P B h P G m h e h B P e S N e e = = (19) where: 0 1 out in 1S S T T G = = optical gain. 2) Analysis of the second term, expressed in ESA-measured noise powers.
48、 Calculate the (frequency-dependent) OA contribution to the measured total noise: in,0 out out shot,0 0 1 0 rin, 1 1 OA,P P T N S S N N N = (20) Summarizing the results for the second term: in,0 out out 1 shot,0 0 0 rin, 1 1 1 1 OA,P P T S N S N S N S N = (21) d) Finally, the noise factor can be calculated on the basis of equation (16) using the results obtained above: + = 1 1 , OA 2 in 2 2 out in 22 2S N P G m P B h B h P m F e e (22) 10 TR 61292-2 IEC:2003(E) 1 1 OA, in 2 in 2 out2S N B h P m P G P F e + = (23) Notice that only ratio type measurements are used in these equati
