> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract— In order to enable new services that require high data rates over longer distances, the optical fiber substitutes the copper cable step by step in the access network area. Time division multiplexed-Passive optical network (TDM-PON) is a fast emerging architecture that uses only passive components between the customer and the central office. PON operators need a monitoring system for the physical layer to guarantee high service quality. This monitoring system is necessary during the fiber installation, final network installation testing, regular operation of the network, and for fault localization. First, in this paper, we present the motivations, requirements and challenges of TDM-PON monitoring. Second, we make an exhaustive review of the monitoring techniques and systems for TDM-PON, mostly proposed within the last five years. In our survey we include the approaches already available in the market even with limited performance and those still in research. Third, we make a detailed classification of all these approaches and qualitatively compare characteristics in a list of performance parameters and aspects. Finally, we outline open issues and future research perspectives in physical layer PON monitoring that may target higher performance, lower cost, or scalability to next generation PON architectures. This includes wavelength division multiplexing (WDM), TDM over WDM or long-reach PONs intended to extend the reach from 20 up to 100 km distances and beyond. Index Terms—PON, FTTH, physical layer, fault detection, fault location, monitoring, OTDR, next generation access. I. INTRODUCTION assive optical networks (PONs) are the most emerging class of fiber access systems in the world today. PON based Fiber-to-the-Home (FTTH) systems are progressively becoming reality while commercial deployments are reported worldwide [1], [2]. FTTH is a network technology that has been recognized as the ultimate solution for providing various communication and multimedia services. This deploys optical fiber cable directly to the home or business to deliver triple- play services, high speed internet access, digital cable television, online gaming, etc. [3]. This worldwide acceleration is largely due to both, the considerable decrease in capital expenditure (CapEx) of introducing FTTH connectivity, and its “future proof” nature in meeting ever Manuscript received ********* ***, 2011. The authors are with Electrical Engineering Department, King Saud University, Saudi Arabia. They are also in Prince Sultan Advanced Technologies Research Institute (PSATRI) and Saudi Telecommunication Company (STC) chair (email: mesmail@ksu.eud.sa, hfathallah@ksu.edu.sa). Habib is also an adjunct professor with the Electrical and Computer Engineering Department of Laval University (Quebec, Canada). increasing user bandwidth requirements [4]. For instance, in February 2010, Google announced the plans to build an experimental Gbps FTTH network to households in North America for testing out new concepts in technologies and applications. Worldwide, FTTH/B (where B stands for building) subscribers attained 44 million at the end of June 2010 out of 121.4 million home already passed, according to a study by IDATE [5]. The time division multiplexing PON (TDM-PON), one among several architectures that can be used in FTTH networks, is widely chosen by operators and it is expected that the next generation 10Gbit TDM-PON will be the most promising system among several technologies [6]. According to Alcatel-Lucent [7], TDM PON bandwidth supply is growing faster than subscriber bandwidth demand. TDM-PON will deliver future ultra-high speed services far more efficiently than WDM-PON for years to come. Such architecture decreases the operational expenditure (OpEx) because there are no electronic components that are more prone to failure in the PON outside plant. Hence, there is no need for the operators to provide and monitor electrical power or maintain back-up batteries in the field. Important FTTH deployments have been carried out in North America, Europe, and Japan over the last decade. Starting from 1:1 (one fiber to one customer) in the early 1990s, passive splitter/combiner (PSC) together with TDM technologies have enabled up to 1:128 for the GPON standard (ITU-T G. 984.1) with forward error correction (FEC). In [8], the authors report a testbed with 1:256 PSC, and future extra large XL-PON systems are aimed at splitting factor of up to 1024 [9]. PON technologies are advancing to increase the data rate to 10 Gbps in parallel with increasing the number of customers to 128 and more. This huge amount of information carried by the PON needs a practical, cost-effective surveillance and management system which is a key factor to continue developing these networks. The International Standards Organization (ISO) categorized the network management (monitoring) functions into five generic categories: performance, configuration, accounting, fault, and security management [10]. In this paper, we discuss only fault management that occurs in the physical layer. Long haul and metro networks use monitoring functions to test the operational status of point-to-point links (P2P). In contrast, a new challenge has been appeared in PON networks. The network now becomes a point-to-multipoint (P2MP) with passive optical splitter placed in the field. This network architecture introduces a new challenge for network testing Physical Layer Monitoring Techniques for TDM-Passive Optical Networks: A Survey Maged Abdullah Esmail, Student Member, IEEE, OSA and Habib Fathallah, Member, IEEE, OSA P