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Tham khảo tài liệu 'advances in optical amplifiers part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 406 Advances in Optical Amplifiers the example being a G-PON with 64 branches logically up to 128 . Basing the PON repeater on optical amplifiers is a promising approach to achieving both longer transmission distances and higher splitting numbers. PON repeater Transmission distance logically depends on ranging discovery method and physically depends on the splitting number and the laser type. Fig. 1. Long-reach PON system with the repeatered system configuration for single fiber wDm I next explain the transmission signals in PON systems. As the downstream optical signal is a continuous wave we can employ an optical amplifier with conventional techniques. In the upstream direction on the other hand as the distances between the OLT and each ONU differ the OLT must be able to receive optical burst signals with different intensities from the ONUs. It is clear that the PON repeater based on optical amplifiers must also be able to amplify these signals without any distortion. However optical burst signal amplification leads to optical surges as shown in Fig.2 which may well cause failure of the optical receiver as well as interfering with the reception of normal signals at the OLT due to gain dynamics. So we have to use burst-mode optical amplifiers to suppress these optical surges and achieve gain stabilization. In this chapter I present burst-mode optical amplifiers for PON systems based on a couple of linear-gain control techniques gain-clamping GC G. Hoven 2002 K-I. Suzuki et. al. 2005 fast automatic gain controlling fast AGC Y. Fukada et. al. 2008 H. Nagaeda et. al. 2008 and fast automatic level controlling fast ALC K-I. Suzuki et. al. 2009 for optical amplifiers. We also discuss the system design based on the signal to noise ratio SNR of the long-reach PON systems K-I. Suzuki et. al. 2006 . On the other hand 10 Gbit s class highspeed PON systems have been receiving great attention which were standardized in IEEE 802.3av and FSAN ITU-T to cover the future demand .
