Fault monitoring and testing in today’s optical access networks

• Main Author: Tay, Benjamin Wei Boon
• Other Authors: Zhong Wende
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics
• Online Access: http://hdl.handle.net/10356/61416
• Institution: Nanyang Technological University

This project investigates the effectiveness of a traditional Optical Time-Domain Reflectometer (OTDR) when it comes to the live monitoring process on a Gigabit Passive Optical Network (GPON) system. An experiment was carried out to determine how well a traditional OTDR can detect the pre-identified factors when it comes to the monitoring of the GPON system. The four factors to be detected in the experiment are, locating of bends and breaks in the optical fiber cable, detecting cables with bad splicing and the usage of dirty connectors. Due to the limitation of the conventional OTDR in a point to multipoint network, the experiment was carried out in a point to point network to improve the accuracy of the faults to be detected. A reference setup was conducted using SM fiber in good working condition and clean connectors. Four other different setups were carried out each with one of the four faults present. The results obtained were compared with that from the reference setup to see if each of the faults can be detected by the OTDR. The outcome of the experiment which will be discussed in greater details later in the report is that the OTDR is not able to detect all the four faults listed. The OTDR measurement display can clearly show the attenuation due to break and dirty connectors but not from macro-bending and bad splicing in the fiber under test. This shows that a conventional OTDR as much as being known as an effective testing optical device, it is still not able to accurately covers all possible factors of attenuation in the fiber cable. In testing a branch of an optical network and finding important parameters such as length of the fiber cable or total attenuation drop, no doubt conventional OTDR is a useful tool to have. But in live monitoring of GPON system where there are multiple branches and various factors resulting in high attenuation loss in the optical network, a conventional OTDR might not be a proven trusted tool as yet. Considering that people all over the world are now moving into the optical network now, it would be of utmost importance that we can come up with a good monitoring system so as to keep the maintenance work efficient and effective.