ALC burst-mode optical fiber amplifiers for 10 Gb/s-class long-reach PONs

This paper proposes a burst-mode optical fiber amplifier (OFA) that consists of a combination of an automatic gain controlled praseodymium-doped fiber amplifier (AGC-PDFA), a fast automatic level controlled circuit (ALC), and a PDFA with just forward pumping. The second PDFA is used as a booster to achieve high gain, over 20 dB. The combination of AGC and ALC techniques suppresses optical surge generation against strong burst signal inputs and also prevents overloading of the burst-mode receivers; it provides OFA-based passive optical network (PON) repeaters with wide input dynamic range and solves the near-far problem in upstream transmission in long-reach PONs. We experimentally compare the operating range of the proposed burst-mode PDFA with that of a conventional burst-mode PDFA. Experiments show that the proposed PDFA achieves a much wider operating area than a conventional PDFA; a wide dynamic range in an access span of 17.5 dB, which is equivalent to the input dynamic range of the burst-mode receiver used in 10 gigabit Ethernet PON (10G-EPON), is obtained with an allowable loss margin of 14 dB in a trunk span. A maximum link budget of 55 dB is achievable.