1、 International Telecommunication Union ITU-T G.666TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2008) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Transmission media and optical systems characteristics Characteristics of optical components and subsystems Characteristi
2、cs of PMD compensators and PMD compensating receivers Recommendation ITU-T G.666 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION
3、 SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHON
4、Y AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 General G.600G.609 Symmetric cable pairs G.610G.619 Land coaxial cable pairs G.620G.629 Submarine cables G.630G.639 Free space optical systems G.640G.649 Optical fibre cables G.650G.659 Characteristics
5、of optical components and subsystems G.660G.679 Characteristics of optical systems G.680G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSM
6、ISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.666 (03/2008) i Recommendation ITU-T G.666 Characteri
7、stics of PMD compensators and PMD compensating receivers Summary Recommendation ITU-T G.666 contains parameters and definitions for devices providing polarization mode dispersion (PMD) compensation needed for transmission and detection of optical signals in a system exhibiting high levels of PMD whi
8、ch would otherwise cause unacceptable levels of system outage. Single and multichannel line PMD compensators are described, as well as single and multichannel PMD compensating receivers. Information on test configurations and implementation options can be found in informative appendices. Source Reco
9、mmendation ITU-T G.666 was approved on 29 March 2008 by ITU-T Study Group 15 (2005-2008) under Recommendation ITU-T A.8 procedure. ii Rec. ITU-T G.666 (03/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The I
10、TU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardi
11、zation Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information tec
12、hnology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compli
13、ance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other oblig
14、atory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementatio
15、n of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of
16、the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to
17、consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2009 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.666 (03/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Terms and defin
18、itions . 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation. 2 4 Abbreviations and acronyms 3 5 Reference configurations 4 5.1 Line PMDCs. 4 5.2 PMDC receivers . 4 6 Parameters of PMDCs 5 Appendix I Measurements of parameters of PMDCs . 9 I.1 Measurement of parameters for PMDC
19、receivers 9 I.2 Measurement of parameters for line PMDCs. 11 I.3 First order dynamic PMD emulator implementation 11 I.4 First and second order PMD emulator implementation . 12 Appendix II Single-channel and multichannel PMDC receiver implementation . 16 II.1 Single-channel PMDC receiver implementati
20、on 16 II.2 Multichannel PMDC receiver implementation 17 Bibliography. 19 Rec. ITU-T G.666 (03/2008) 1 Recommendation ITU-T G.666 Characteristics of PMD compensators and PMD compensating receivers 1 Scope This Recommendation contains parameters and definitions for devices providing polarization mode
21、dispersion (PMD) compensation needed for transmission and detection of optical signals in a system exhibiting high levels of PMD. The PMD compensating devices described include both single and multichannel applications. This Recommendation defines requirements and key parameters for first and higher
22、 order PMD compensators (PMDCs) and includes dynamic PMD characteristics. This Recommendation distinguishes line PMDCs from PMDC receivers which may comprise electrical as well as optical forms of PMD compensation. Measurement methods for PMD-related impairments can be found in ITU-T G.650.2 2 Refer
23、ences The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; user
24、s of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommend
25、ation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.650.2 Recommendation ITU-T G.650.2 (2005), Definitions and test methods for statistical and non-linear related attributes of single-mode fibre and cable. ITU-T G.652 Recommendation ITU-T G.652 (2005), Characte
26、ristics of a single-mode optical fibre and cable. ITU-T G.653 Recommendation ITU-T G.653 (2003), Characteristics of a dispersion-shifted single-mode optical fibre and cable. ITU-T G.654 Recommendation ITU-T G.654 (2004), Characteristics of a cut-off shifted single-mode optical fibre and cable. ITU-T
27、 G.655 Recommendation ITU-T G.655 (2003), Characteristics of a non-zero dispersion-shifted single-mode optical fibre and cable. ITU-T G.656 Recommendation ITU-T G.656 (2004), Characteristics of a fibre and cable with non-zero dispersion for wideband optical transport. ITU-T G.661 Recommendation ITU-
28、T G.661 (1998), Definition and test methods for the relevant generic parameters of optical amplifier devices and subsystems. ITU-T G.662 Recommendation ITU-T G.662 (2005), Generic characteristics of optical amplifier devices and subsystems. ITU-T G.665 Recommendation ITU-T G.665 (2005), Generic char
29、acteristics of Raman amplifiers and Raman amplified subsystems. ITU-T G.671 Recommendation ITU-T G.671 (2005), Transmission characteristics of optical components and subsystems. ITU-T G.694.1 Recommendation ITU-T G.694.1 (2002), Spectral grids for WDM applications: DWDM frequency grid. 2 Rec. ITU-T
30、G.666 (03/2008) ITU-T G.698.1 Recommendation ITU-T G.698.1 (2006), Multichannel DWDM applications with single-channel optical interfaces. 3 Terms and definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 differential group delay (DGD): ITU-T G.
31、650.2, symbol . 3.1.2 polarization dispersion vector (PDV): ITU-T G.650.2, symbol r. NOTE In a former version of this Recommendation, PDV was called “First order DGD vector“. The renaming is due to an alignment of terms with respect to ITU-T G.650.2. 3.1.3 principle state of polarization vector: ITU
32、-T G.650.2, symbol pr. 3.1.4 ripple: ITU-T G.671. 3.1.5 spectral excursion: ITU-T G.698.1. 3.1.6 Stokes vector: ITU-T G.650.2, Symbol sv. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 DGD rate of change: The DGD rate of change is defined as the absol
33、ute value of the derivative of the DGD with respect to time, i.e., t, and is measured in ps/ms. 3.2.2 OSNR penalty due to DGD: An optical signal that has been subject to a DGD requires a larger OSNR at the receiver to achieve BER = 1012than an optical signal which has not been affected by DGD (i.e.,
34、 = 0), assuming the same receiver input power in both cases. This OSNR difference is called the OSNR penalty due to DGD. In this case no SOPMD is considered. NOTE For applications where FEC bytes are required to be transmitted, the BER of 1012is required to be met only after the error correction (if
35、 used) has been applied. The BER at the input of the FEC decoder for these cases can therefore be significantly higher than 1012. 3.2.3 polarization rotation speed (PRS): The polarization rotation speed is the absolute value of the temporal change of the Stokes vector sr, i.e., tsPRS=r, and is measu
36、red in rad/ms. 3.2.4 PMDC receiver sensitivity: The value of mean received power at point MPI-R to achieve the specified BER. This must be met across all states of input polarization with a worst-case transmitter, but does not have to be met with degradations of the optical path other than the PMD.
37、3.2.5 PSP rate of change: The PSP rate of change is defined as the derivative of the principle state of polarization vector p in Stokes space with respect to time, i.e., tp, and is measured in rad/ms. 3.2.6 second-order PMD (SOPMD): Second-order PMD is defined by += ppSOPMDrrr. This is the derivativ
38、e of the PDV (first-order DGD vector) with respect to the optical frequency . The SOPMD consists of two terms, namely pr and pr. The first term, pr , represents the polarization-dependent chromatic dispersion term (PCD), Rec. ITU-T G.666 (03/2008) 3 while pris the so-called depolarization term (DEPO
39、L) which describes the PSP unit vector rotation with respect to frequency (at the centre frequency of the signal). The corresponding magnitudes of these quantities are given as follows: Magnitude of the SOPMD = r, magnitude of the depolarization = pr, magnitude of the PCD = . 4 Abbreviations and acr
40、onyms This Recommendation uses the following abbreviations and acronyms: BER Bit Error Ratio DEMUX Demultiplexer DEPOL Depolarization term DGD Differential Group Delay LPMDC Line Polarization Mode Dispersion Compensator M-LPMDC Multichannel Line Polarization Mode Dispersion Compensator M-PMDC-Rx Mul
41、tichannel Polarization Mode Dispersion Compensating Receiver MPI Main Path Interface MUX Multiplexer NRZ Non-Return to Zero OA Optical Amplifier O-E-O Optical-Electrical-Optical (conversion) OSNR Optical Signal-to-Noise Ratio PCD Polarization-dependent Chromatic Dispersion PDL Polarization Dependent
42、 Loss PDV Polarization Dispersion Vector PMD Polarization Mode Dispersion PMDC Polarization Mode Dispersion Compensator PMDC-Rx Polarization Mode Dispersion Compensating Receiver PRBS Pseudo-Random Binary Sequence PRS Polarization Rotation Speed PSP Principle State of Polarization RZ Return to Zero
43、S-LPMDC Single-Channel Line Polarization Mode Dispersion Compensator S-PMDC-Rx Single-Channel Polarization Mode Dispersion Compensating Receiver SOP State of Polarization SOPMD Second Order Polarization Mode Dispersion WDM Wavelength Division Multiplexing 4 Rec. ITU-T G.666 (03/2008) 5 Reference con
44、figurations PMDCs are intended to be used in optical transmission systems in order to reduce PMD-induced signal degradations. Therefore, characteristics of PMDCs must be considered, at least in part, in conjunction with a whole transmission system. A generic configuration of a transmission system wi
45、th PMDC(s) is shown in Figure 5-1. It consists of a transmitter terminal, a receiver terminal and a transmission link in between with optional line PMDC(s). A single-channel system contains a single-channel transmitter and receiver terminal while a multichannel transmitter and receiver terminal is u
46、sed in a multichannel system. The receiver terminal can also contain optional PMDC functionalities and is called a “PMDC receiver“ in this case. In the following clauses, optical line PMDCs (LPMDC) are distinguished from PMDC receivers. A black box approach is applied for the PMDCs and PMDC receiver
47、s. Monitoring and control (if present) is included in the black box. Figure 5-1 Generic configuration of a transmission system with PMDCs 5.1 Line PMDCs Line PMDCs have an optical input and an optical output port and no O-E-O conversion is performed inside a line PMDC. A single-channel line PMDC (S-
48、LPMDC) can handle a single-channel optical signal, while a multichannel line PMDC (M-LPMDC) is constructed for a multichannel optical signal. Both types are illustrated schematically in Figures 5-2 and 5-3, respectively. Figure 5-2 Reference configuration of a single-channel line PMDC (S-LPMDC) Figu
49、re 5-3 Reference configuration of a multichannel line PMDC (M-LPMDC) 5.2 PMDC receivers In the case of PMDC receivers (PMDC-Rx), the PMDC functionality is embedded in the receiver terminal. There are a number of options regarding how to realize PMDC receivers. Single-channel PMDC receivers are distinguished from multichannel PMDC receivers. A schematic diagram of a single-channel PMDC receiver (S-PMDC-Rx) is shown in Figure 5-4. A single-channel optical signa
