Optical Distribution Network

FTTH - Optical Distribution Network

Comparison of ODN Class A, B, and C Optics

In this chapter, let us understand what Split Ratios, Maximum Reach and Traffic Management are in the Optical Distribution Network (ODN).

The maximum permissible optical power attenuation between OLT optical ports to ONT input is 28dB, which is by utilizing the so-called Class B optical network elements. ODN Class A, B, and C are differentiated mainly on the ‘optical transmitter power output’ and ‘bit-rate optical receiver sensitivity.’ Class A gives the least optical-budget and Class C gives the highest, while cost wise they are in the same order. For maximum 1:64 split ratio, Class B optics is commonly deployed on commercial basis.

The comparison of class A, B, and C ODN optics is shown in the table given below −

S.No. Parameter Unit Class A Class B Class C Remarks
1 Attenuation range (ITU-T Rec. G.982) dB 5 – 20 10 – 25 15 – 30
2 2488 Mbps downstream direction
2.1 OLT Transmitter
2.1.1 Mean launched power MIN dBm 0 +5 +3 Single fiber
2.1.2 Mean launched power MAX dBm +4 +9 +7 Single fiber
2.1.3 Mean launched power MIN dBm 0 +5 +3 Dual fiber
2.1.4 2.1.4 Mean launched power MAX dBm +4 +9 +7 Dual fiber
2.2 ONU Receiver
2.2.1 Minimum sensitivity dBm -21 -21 -28 Single fiber
2.2.2 Minimum overload dBm -1 -1 -8 Single fiber
2.2.3 Minimum sensitivity dBm -21 -21 -28 Dual fiber
2.2.4 Minimum overload dBm -1 -1 -8 Dual fiber
3 1244 Mbps upstream direction
3.1 ONU Transmitter
3.1.1 Mean launched power MIN dBm -3 -2 +2 Single fiber
3.1.2 Mean launched power MAX dBm +2 +3 +7 Single fiber
3.1.3 Mean launched power MIN dBm -3 -2 +2 Dual fiber
3.1.4 Mean launched power MAX dBm +2 +3 +7 Dual fiber
3.2 OLT Receiver
3.2.1 Minimum sensitivity dBm -24 -28 -29 Single fiber
3.2.2 Minimum overload dBm -3 -7 -8 Single fiber
3.2.3 Minimum sensitivity dBm -24 -28 -29 Dual fiber
3.2.4 Minimum overload dBm -3 -7 -8 Dual fiber