I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU U n i o n G.640 (03/2006) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Transmission media characteristics – Submarine cables Co-location longitudinally compatible interfaces for free space optical systems ITU-T Recommendation G.640 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIERTRANSMISSION SYSTEMS INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TRANSMISSION MEDIA CHARACTERISTICS General Symmetric cable pairs Land coaxial cable pairs Submarine cables Optical fibre cables Characteristics of optical components and subsystems DIGITAL TERMINAL EQUIPMENTS DIGITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS TRANSMISSION MEDIA CHARACTERISTICS DATA OVER TRANSPORT – GENERIC ASPECTS ETHERNET OVER TRANSPORT ASPECTS ACCESS NETWORKS For further details, please refer to the list of ITU-T Recommendations. G.100–G.199 G.200–G.299 G.300–G.399 G.400–G.449 G.450–G.499 G.600–G.699 G.600–G.609 G.610–G.619 G.620–G.629 G.630–G.649 G.650–G.659 G.660–G.699 G.700–G.799 G.800–G.899 G.900–G.999 G.1000–G.1999 G.6000–G.6999 G.7000–G.7999 G.8000–G.8999 G.9000–G.9999 ITU-T Recommendation G.640 Co-location longitudinally compatible interfaces for free space optical systems Summary This Recommendation provides a procedure for establishing that two co-located Free Space Optical (FSO) transmission systems will not interfere with each other. Calculations of the conditions required to be met to prevent interference in some examples of co-located FSO systems are also included. Source ITU-T Recommendation G.640 was approved on 29 March 2006 by ITU-T Study Group 15 (2005-2008) under the ITU-T Recommendation A.8 procedure. ITU-T Rec. G.640 (03/2006) i FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU 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 Standardization 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 technology which fall within ITU-T's 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. Compliance 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 obligatory 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 implementation 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 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, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2006 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ii ITU-T Rec. G.640 (03/2006) CONTENTS Page 1 Scope ..................................................................