Novel Fault Monitoring Scheme for TDM-PON Systems

• Main Authors: Shuen-te Ji, 紀順得
• Other Authors: San-Liang Lee
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/81655788045753672139

碩士 === 國立臺灣科技大學 === 電子工程系 === 96 === Passive optical networks (PONs) are becoming the popular solutions for access networks due to the advantages of low cost, large capacity, and easy maintenance. For enhancing the survivability, the PON system must have fault detection capability. Because a PON system has a point-to-multipoint topology, the backscattered signals from the distribution fibers overlap together, making the fault detection difficult by using the conventional optical time domain reflectometer (OTDR). To monitor the failure of distribution fibers, a tunable light source at the central office (CO) and a fiber Bragg grating (FBG) at each optical network unit (ONU) was demonstrated. However, this monitoring system is not cost-effective because of the use of OSA, and FBGs. The FBG is difficult to be mass produced or integrated with other active and passive components in order to further reduce the cost of ONUs. Therefore, we propose a new monitoring scheme that employs a continuous wavelength sweeper at the CO and an interferometric (IF) device at each ONU. The CO send a frequency-modulation signal and then the IF devices reflect the interference signal to the CO. The reflected signal from each ONU can easily be distinguished from the others by performing a Fourier transform. The corresponding spectral component will disappear if one of the distribution fiber is broken. This scheme provides versatility for fault monitoring by using low-cost and mass-producible components. We will discuss the performance by using different IF device at ONUs. The effect of sweeper light source, the design of the receiver circuit, and the sensitivity and linearity of this monitoring system will be investigated in detailed. Also, we discuss the advantages and drawbacks between the proposed monitoring scheme and the OTDR and optical frequency domain reflectometer (OFDR) schemes.