This Recommendation describes a flexible optical fibre access network capable of supporting the bandwidth requirements of narrow-band and broadband services. This Recommendation describes systems with nominal downstream line rates of 155.52, 622.08 and 1244.16 Mbit/s, and nominal upstream line rates of 155.52 and 622.08 Mbit/s. Both symmetrical and asymmetrical systems are described. This Recommendation proposes the physical layer requirements and specifications for the physical media dependent layer, the TC layer and the ranging protocol of an ATM-based Broadband Passive Optical Network (B-PON). This revised version of G.983.1 incorporates the material from: G.983.1 (1998), G.983.1 Cor. 1 (1999), G.983.1 Amd.1 (2001), G.983.1 Cor. 1 Erratum 1(2002), G.983.1 Amd.2 (2003), G.983.1 Implementor's Guide (2003).